ORCID Profile
0000-0003-1315-3797
Current Organisation
University of Queensland
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In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Animal Physiological Ecology | Physiology | Comparative Physiology | Ecology | Zoology Not Elsewhere Classified | Zoology | Ecological Physiology | Environmental Science and Management | Comparative Physiology | Conservation and Biodiversity | Freshwater Ecology | Animal Anatomy And Histology | Fish physiology and genetics | Physiology Not Elsewhere Classified | Fisheries Sciences | Hydrology | Aquaculture | Global Change Biology | Ecohydrology | Ecological Impacts of Climate Change | Ecosystem Function | Environmental Management | Marine And Estuarine Ecology (Incl. Marine Ichthyology) | Ecological impacts of climate change and ecological adaptation | Environmental Rehabilitation (excl. Bioremediation) | Conservation And Biodiversity | Behavioural Ecology | Freshwater Ecology
Biological sciences | Expanding Knowledge in the Biological Sciences | Fresh, Ground and Surface Water Flora, Fauna and Biodiversity | Ecosystem Adaptation to Climate Change | Living resources (flora and fauna) | Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments | Land and water management | Land and Water Management of environments not elsewhere classified | Sparseland, Permanent Grassland and Arid Zone Flora, Fauna and Biodiversity | Living resources (flora and fauna) | Aquaculture | Fish |
Publisher: Springer Science and Business Media LLC
Date: 12-1987
DOI: 10.1007/BF00297069
Publisher: The Company of Biologists
Date: 08-2020
DOI: 10.1242/JEB.232892
Publisher: Wiley
Date: 18-08-2016
Publisher: Wiley
Date: 04-01-2010
Publisher: Wiley
Date: 24-05-2012
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.CBPA.2015.09.007
Abstract: Temperature and ultraviolet radiation (UVR) are key environmental drivers that are linked in their effects on cellular damage. Exposure to both high temperatures and UVR can cause cellular damage that result in the up-regulation of common protective mechanisms, such as the induction of heat shock proteins (Hsps) and antioxidants. As such, the interactive effects of these stressors at the cellular level may determine physiological limits, such as thermal tolerance. Furthermore, antioxidant activity is often thermally sensitive, which may lead to temperature dependent effects of UVR exposure. Here we examined the interactive effects of temperature and UVR on upper thermal limits, Hsp70 abundance, oxidative damage and antioxidant (catalase) activity. We exposed Limnodynastes peronii tadpoles to one of three temperature treatments (constant 18°C, constant 28°C and daily fluctuations between 18 and 28°C) in the presence or absence of UVR. Tadpoles were tested for upper thermal limits (CTmax), induction of Hsp70, oxidative damage and catalase activity. Our results show that CTmax was influenced by an interactive effect between temperature and UVR treatment. For tadpoles kept in cold temperatures, exposure to UVR led to cross-tolerance to high temperatures, increasing CTmax. Plasticity in this trait was not fully explained by changes in the lower level mechanistic traits examined. These results highlight the difficulty in predicting the mechanistic basis for the interactive effects of multiple stressors on whole animal traits. Multifactorial studies may therefore be required to understand how complex mechanistic processes shape physiological tolerances, and determine responses to environmental variation.
Publisher: Wiley
Date: 21-03-2016
Publisher: Elsevier BV
Date: 05-2010
DOI: 10.1016/J.CBPA.2009.12.009
Abstract: The thermal dependence of aerobic metabolic rate in air-breathing ectotherms indicates that an increase in temperature will reduce e duration. The ability, however, to extract oxygen from the water provides an additional means to maintain aerobic metabolism and prolong submergence. Therefore, we hypothesised that as temperature increased, a bimodally respiring animal will compensate for the effects on aerobic metabolic rate by increasing aquatic oxygen uptake. The fully aquatic, bimodally respiring Arafura filesnake (Acrochordus arafurae) was used to determine how temperature affects the partitioning of oxygen exchange between aerial and aquatic sources and the impacts on e duration. We found that rate of oxygen consumption increased with temperature (Q(10 (20-32 degrees C))=2.52) but aquatic oxygen uptake remained temperature independent and all extra oxygen demands were met by increasing aerial gas exchange, thus reducing e duration. Maximum e duration reduced from 77 min to 28 min between 20 degrees C and 32 degrees C. Under severe hypoxia, oxygen uptake from the water was negligible and e duration was further reduced to 21 min at 32 degrees C. Despite e duration being reduced as the water temperature increased, aquatic oxygen uptake was still responsible for significantly prolonging e duration.
Publisher: Wiley
Date: 08-12-2014
DOI: 10.1111/AEC.12212
Publisher: Elsevier BV
Date: 2003
Publisher: University of Chicago Press
Date: 2005
DOI: 10.1086/425192
Abstract: The differences in physical properties of air and water pose unique behavioural and physiological demands on semiaquatic animals. The aim of this study was to describe the ing behaviour of the freshwater crocodile Crocodylus johnstoni in the wild and to assess the relationships between ing, body temperature, and heart rate. Time-depth recorders, temperature-sensitive radio transmitters, and heart rate transmitters were deployed on each of six C. johnstoni (4.0-26.5 kg), and data were obtained from five animals. Crocodiles showed the greatest ing activity in the morning (0600-1200 hours) and were least active at night, remaining at the water surface. Surprisingly, activity pattern was asynchronous with thermoregulation, and activity was correlated to light rather than to body temperature. Nonetheless, crocodiles thermoregulated and showed a typical heart rate hysteresis pattern (heart rate during heating greater than heart rate during cooling) in response to heating and cooling. Additionally, e length decreased with increasing body temperature. Maximum ing length was 119.6 min, but the greatest proportion of ing time was spent on relatively short (<45 min) and shallow (<0.4 m) es. A bradycardia was observed during ing, although heart rate during submergence was only 12% lower than when animals were at the surface.
Publisher: Oxford University Press (OUP)
Date: 2018
Publisher: Wiley
Date: 05-1993
Publisher: Elsevier BV
Date: 09-2000
DOI: 10.1016/S1095-6433(00)00238-5
Abstract: Despite several studies on adult hibians, only larvae of the striped marsh frog (Limnodynastes peronii) have been reported to possess the ability to compensate for the effects of cool temperature on locomotor performance by thermal acclimation. In this study, we investigated whether this thermal acclimatory ability is shared by adult L. peronii. We exposed adult L. peronii to either 18 or 30 degrees C for 8 weeks and tested their swimming and jumping performance at six temperatures between 8 and 35 degrees C. Acute changes in temperature affected both maximum swimming and jumping performance, however there was no difference between the two treatment groups in locomotor performance between 8 and 30 degrees C. Maximum swimming velocity of both groups increased from 0.62+/-0.02 at 8 degrees C to 1.02+/-0.03 m s(-1) at 30 degrees C, while maximum jump distance increased from approximately 20 to >60 cm over the same temperature range. Although adult L. peronii acclimated to 18 degrees C failed to produce a locomotor response at 35 degrees C, this most likely reflected a change in thermal tolerance limits with acclimation rather than modifications in the locomotor system. As all adult hibians studied to date are incapable of thermally acclimating locomotor performance, including adults of L. peronii, this acclimatory capacity appears to be absent from the adult stage of development.
Publisher: Springer Science and Business Media LLC
Date: 10-07-1998
Publisher: The Company of Biologists
Date: 20-07-2012
DOI: 10.1242/BIO.2012950
Abstract: For the embryos and tadpoles of hibian species, exposure to ultraviolet-B radiation (UVBR) can be lethal, or cause a variety of sublethal effects. Low temperatures enhance the detrimental effects of UVBR and this is most likely because the enzyme-mediated processes involved in the repair of UVBR-induced damage function less effectively at low temperatures. Whether these repair processes are also impaired, and thus the negative effects of UVBR similarly enhanced, at high temperatures is not known, but is an ecologically relevant question to ask given that organisms that inhabit environments where the temperature fluctuates widely on a daily timescale are likely to experience high doses of UVBR when temperatures are high. Here we examined the thermal-dependence of UVBR effects in the context of an ecologically-relevant fluctuating UVBR and temperature regime to test the hypothesis that exposure to peak UVBR levels while the temperature is high (35°C) is more detrimental to embryonic and larval Limnodynastes peronii than exposure to peak UVBR levels while the temperature is moderate (25°C). Embryos exposed to peak UVBR levels at 35°C hatched 10 h later than those exposed to peak UVBR levels at 25°C and, as tadpoles, were smaller and consequently swam more slowly but, in an environment with predators, exhibited no difference in survival time. There was also no effect of experimental treatment on the hatching success of embryos, nor on the post-hatch survival of tadpoles. These findings, therefore, are not sufficiently strong to support our hypothesis that high temperatures enhance the negative effects of UVBR in embryonic and larval hibians.
Publisher: Elsevier BV
Date: 07-2004
Publisher: The Royal Society
Date: 06-02-2019
Abstract: Amphibian skin is highly variable in structure and function across anurans, and plays an important role in physiological homeostasis and immune defence. For ex le, skin sloughing has been shown to reduce pathogen loads on the skin, such as the lethal fungus Batrachochytrium dendrobatidis ( Bd ), but interspecific variation in sloughing frequency is largely unknown. Using phylogenetic linear mixed models, we assessed the relationship between skin turnover rate, skin morphology, ecological traits and overall evidence of Bd -driven declines. We examined skin sloughing rates in 21 frog species from three continents, as well as structural skin characteristics measured from preserved specimens. We found that sloughing rate varies significantly with phylogenetic group, but was not associated with evidence of Bd -driven declines, or other skin characteristics examined. This is the first comparison of sloughing rate across a wide range of hibian species, and creates the first database of hibian sloughing behaviour. Given the strong phylogenetic signal observed in sloughing rate, approximate sloughing rates of related species may be predicted based on phylogenetic position. While not related to available evidence of declines, understanding variation in sloughing rate may help explain differences in the severity of infection in genera with relatively slow skin turnover rates (e.g. Atelopus ).
Publisher: The Royal Society
Date: 09-2014
Abstract: Levels of UVB radiation (UVB) and mean temperatures have increased substantially over recent decades in many regions of the world. Both stressors independently can compromise immune function, disease resistance and fitness in fish. The impact of UVB can also be exacerbated by interactions with environmental temperatures. In this paper, we test the hypothesis that UVB and temperature act synergistically to influence patterns of energy consumption and susceptibility to disease. We exposed mosquitofish, Gambusia holbrooki , to a factorial design of low and high UVB levels and low (18°C) and high (25°C) temperatures. The combination of high UVB and high temperature interacted synergistically to suppress metabolism and exacerbate infection intensity by the fish pathogen whitespot ( Ichtyhophthirius multifiliis ). Given the rapid changes in the thermal environment globally, the interaction between UVB and temperatures on energy use and disease resistance could pose significant problems for aquatic animal health in the context of both pre-existing and emerging diseases.
Publisher: Elsevier BV
Date: 05-1992
DOI: 10.1016/0300-9629(92)90007-D
Abstract: 1. Voluntary undisturbed es by Crocodylus porosus were short in duration (3.08 +/- 1.87 min, mean +/- SD) and accompanied by a small but significant bradycardia (14.3 +/- 5.9% drop). 2. When crocodiles were disturbed underwater there was a rapid onset of "fright" bradycardia, to 65 +/- 6.0% of surface heart rates and e durations were prolonged to 19.6 +/- 1.8 min. 3. The development of "fright" bradycardia was not accompanied by any increase in intratracheal pressure or expulsion of lung gas. However, sustained contraction of the abdomen and expansion of the thorax revealed a redistribution of air anteriorly within the lungs. 4. We propose that the redistribution of air within the lungs may generate an afferent signal which potentiates the initiation of a severe, e-prolonging bradycardia.
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/MF16124
Abstract: Facultative air-breathing fish can persist in hypoxic waters due to their capacity to acquire atmospheric oxygen. Most studies examining responses of air-breathing fish to aquatic hypoxia have occurred under experimental conditions. How air-breathing fish respond to hypoxic conditions in the field has received less attention. Using depth sensor transmitters and an array of acoustic receivers to monitor the facultative air-breathing Australian lungfish (Neoceratodus forsteri), we investigated habitat preferences and behavioural responses to seasonal hypoxic zones in a riverine impoundment. Three-dimensional (3-D) kernel utilisation distribution (KUD) models revealed that during stratified conditions, lungfish remained above the oxycline, rarely venturing into hypoxic waters, whereas during holomixis lungfish used a wider range of depths. Total volumetric space utilisation did not change significantly during stratified periods, but the distribution of space used changed, constrained by the oxycline. Despite N. forsteri having lungs to supplement oxygen requirements, the presence of a hypoxic zone constrained the core (50% 3-D-KUD) volumetric space used by lungfish to .6% of the total available space of the study area. With increasing demand for new impoundments in many tropical and subtropical regions, the present study provides insights to how air-breathing fish species may respond to altered riverine conditions from impoundments.
Publisher: Elsevier BV
Date: 08-1994
Publisher: Springer Science and Business Media LLC
Date: 24-09-1999
Abstract: Previous analyses of thermal acclimation of locomotor performance in hibians have only examined the adult life history stage and indicate that the locomotor system is unable to undergo acclimatory changes to temperature. In this study, we examined the ability of tadpoles of the striped marsh frog (Limnodynastes peronii) to acclimate their locomotor system by exposing them to either 10 degrees C or 24 degrees C for 6 weeks and testing their burst swimming performance at 10, 24, and 34 degrees C. At the test temperature of 10 degrees C, maximum velocity (Umax) of the 10 degrees C-acclimated tadpoles was 47% greater and maximum acceleration (Amax) 53% greater than the 24 degrees C-acclimated animals. At 24 degrees C, Umax was 16% greater in the 10 degrees C-acclimation group, while there was no significant difference in Amax or the time taken to reach Umax (T-Umax). At 34 degrees C, there was no difference between the acclimation groups in either Umax or Amax, however T-Umax was 36% faster in the 24 degrees C-acclimation group. This is the first study to report an hibian (larva or adult) possessing the capacity to compensate for cool temperatures by thermal acclimation of locomotor performance. To determine whether acclimation period affected the magnitude of the acclimatory response, we also acclimated tadpoles of L. peronii to 10 degrees C for 8 months and compared their swimming performance with tadpoles acclimated to 10 degrees C for 6 weeks. At the test temperatures of 24 degrees C and 34 degrees C, Umax and Amax were significantly slower in the tadpoles acclimated to 10 degrees C for 8 months. At 10 degrees C, T-Umax was 40% faster in the 8-month group, while there were no differences in either Umax or Amax. Although locomotor performance was enhanced at 10 degrees C by a longer acclimation period, this was at the expense of performance at higher temperatures.
Publisher: Wiley
Date: 10-1990
Abstract: Sockeye salmon were transferred rapidly from freshwater to seawater and the changes in gill morphology, in particular the distribution and sizes of chloride and mucous cells on the afferent filamental surface examined. Salmon that successfully adapted to seawater were compared with salmon that did not adapt to seawater and died as a consequence of osmoregulatory failure. The number of mucus cells (density), determined from scanning electron microscopy, increased significantly after seawater challenge. A greater increase in mucus cell density occurred in the salmon that failed to adapt to seawater. Light microscopy of transverse sections of gills detected no difference in mucus cell numbers after seawater challenge. It is proposed that mucus cells that lie just beneath the gill epithelium are activated in response to the seawater challenge, and migrate and open onto the epithelium. Freshwater-adapted salmon that had low densities of chloride cells prior to the seawater challenge failed to adapt, whereas salmon that had high densities of chloride cells adapted successfully to seawater. In the latter, the density of chloride cells on the afferent surface decreased after 30 days in seawater. The apical surface of the chloride cells of freshwater-adapted sockeye were either smooth or covered with microvilli. A greater proportion of microvilli-covered chloride cells occurred in the freshwater-adapted salmon that subsequently adapted to seawater.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 08-01-2016
Publisher: The Company of Biologists
Date: 2016
DOI: 10.1242/JEB.131615
Abstract: Ultraviolet B radiation (UV-B) can reduce swimming performance by increasing reactive oxygen species (ROS) formation. High concentrations of ROS can damage mitochondria resulting in reduced ATP production. ROS can also damage muscle proteins thereby leading to impaired muscle contractile function. We have shown previously that UV-B exposure reduces locomotor performance in mosquitofish (Gambusia holbrooki) without affecting metabolic scope. Our aim was therefore to test whether UV-B influences swimming performance of mosquitofish by ROS-induced damage to muscle proteins without affecting mitochondrial function. In a fully factorial design, we exposed mosquitofish to UV-B and no-UV-B controls in combination with exposure to N-acetylcysteine (NAC) plus no-NAC controls. We used NAC, a precursor of glutathione, as an antioxidant to test whether any effects of UV-B on swimming performance were at least partly due to UV-B-induced ROS. UV-B significantly reduced critical sustained swimming performance and tail beat frequencies, and it increased ROS-induced damage (protein carbonyl concentrations and lipid peroxidation) in muscle. However, UV-B did not affect the activity of sarco-endoplamic reticulum ATPase (SERCA), an enzyme associated with muscle calcium cycling and muscle relaxation. UV-B did not affect ADP phosphorylation (state 3) rates of mitochondrial respiration, and it did not alter the amount of ATP produced per atom of oxygen consumed (P:O ratio). However, UV-B reduced the mitochondrial respiratory control ratio. Under UV-B exposure, fish treated with NAC showed greater swimming performance and tail beat frequencies, higher glutathione concentrations, lower protein carbonyl concentrations and lipid peroxidation than untreated fish. Tail beat litude was not affected by any treatment. Our results showed, firstly, that the effects of UV-B on locomotor performance were mediated by ROS and, secondly, that reduced swimming performance is not caused by impaired mitochondrial ATP production. Instead, reduced tail beat frequencies indicate that muscle of UV-B exposed fish were slower, which was likely to have been caused by slower contraction rates, because SERCA activities remained unaffected.
Publisher: Inter-Research Science Center
Date: 19-11-2012
DOI: 10.3354/DAO02523
Abstract: The emergence of disease as a significant global threat to hibian ersity has generated considerable interest in hibian defenses against cutaneous microbial infection and disease. To date, however, the influence of sloughing on the susceptibility of hibians to infection and disease has been largely overlooked. To investigate the potential for sloughing to regulate topical microbial loads, the abundance of cultivable cutaneous bacteria and fungi in the cane toad Rhinella marina were compared before and after sloughing. Toads were also exposed to fluctuating thermal regimes (10-20 and 20-30°C) and variable photoperiods to investigate possible effects of season and climate on sloughing periodicity. Sloughing substantially reduced the abundance of cultivable cutaneous bacteria and fungi by up to 100%. The intermoult interval of toads maintained at 10-20°C was twice that of animals at 20-30°C and did not appear to thermally acclimate. Photoperiod had no discernable influence on sloughing periodicity. Results of this study suggest that normal sloughing cycles could play a significant role in controlling the persistence and build-up of cutaneous microbes, including pathogens. The loss of non-pathogenic commensal and protective skin microbiota after sloughing may also influence host susceptibility to cutaneous pathogens. We suggest that the spatio-temporal dynamics of chytridiomycosis, the widespread and often fatal disease caused by the fungal pathogen Batrachochytrium dendrobatidis, are related to temperature not only because of its effect on the growth of the fungus, but also because of its effect on the frequency of host sloughing.
Publisher: Wiley
Date: 20-03-2009
Publisher: Wiley
Date: 07-06-2010
DOI: 10.1111/J.1365-2656.2010.01709.X
Abstract: 1. The estuarine crocodile (Crocodylus porosus) is the world's largest living reptile. It predominately inhabits freshwater and estuarine habitats, but widespread geographic distribution throughout oceanic islands of the South-east Pacific suggests that in iduals undertake sizeable ocean voyages. 2. Here we show that adult C. porosus adopt behavioural strategies to utilise surface water currents during long-distance travel, enabling them to move quickly and efficiently over considerable distances. 3. We used acoustic telemetry to monitor crocodile movement throughout 63 km of river, and found that when in iduals engaged in a long-distance, constant direction journey (>10 km day(-1)), they would only travel when current flow direction was favourable. Depth and temperature measurements from implanted transmitters showed that they remained at the water surface during travel but would e to the river substratum or climb out on the river bank if current flow direction became unfavourable. 4. Satellite positional fixes from tagged crocodiles engaged in ocean travel were overlaid with residual surface current (RSC) estimates. The data showed a strong correlation existed between the bearing of the RSC and that of the travelling crocodile (r(2) = 0.92, P < 0.0001). 5. The study demonstrates that C. porosus dramatically increase their travel potential by riding surface currents, providing an effective dispersal strategy for this species.
Publisher: Springer Science and Business Media LLC
Date: 18-03-2010
DOI: 10.1007/S00360-010-0464-Z
Abstract: Salt and water balance in the estuarine crocodile, Crocodylus porosus, involves the coordinated action of both renal and extra-renal tissues. The highly vascularised, lingual salt glands of C. porosus excrete a concentrated sodium chloride solution. In the present study, we examined the in vivo actions of vasoactive intestinal peptide (VIP), B-type natriuretic peptide (BNP) and angiotensin II (ANG II) on the secretion rate and blood perfusion of the lingual salt glands. These peptides were selected for their vasoactive properties in addition to their reported actions on salt gland activity in birds and turtles and rectal gland activity in elasmobranchs. The femoral artery was cannulated in seven juvenile crocodiles for delivery of peptides and measurement of mean blood pressure and heart rate. In addition, secretion rate of, and blood flow to, the salt glands were recorded simultaneously using laser Doppler flowmetry. VIP stimulated salt secretion was coupled to an increase in blood flow and vascular conductance of the lingual salt glands. BNP was a potent stimulant of salt gland secretion, resulting in a maximal secretion rate of more than 15-fold higher than baseline however, this was not coupled to an increase in perfusion rate, which remained unchanged. ANG II failed to stimulate salt gland secretion and there was a transient decrease in salt gland blood flow and vascular conductance. It is evident from this study that blood flow to, and secretion rate from, the lingual salt glands of C. porosus are regulated independently indeed, it is apparent that maximal secretion from the salt glands may not require maximal blood flow.
Publisher: The Company of Biologists
Date: 15-07-2009
DOI: 10.1242/JEB.028233
Abstract: During dormancy energy conservation is a key priority and as such dormant animals undergo a major metabolic depression to conserve their limited endogenous fuel supplies. Mitochondrial coupling efficiency, the efficiency with which mitochondria convert oxygen into ATP, significantly affects aerobic metabolism and thus to maximise energy savings during dormancy it has been hypothesised that coupling efficiency should increase. However, previous studies have shown coupling efficiency to be maintained or even to decrease. In this study we measured state 3 and state 4 mitochondrial respiration in the muscle of the burrowing frog, Cyclorana alboguttata and calculated the respiratory control ratio as a measure of coupling efficiency. After 7 months in aestivation, C. alboguttata significantly reduced oxygen consumption of isolated mitochondria by 83% and, unlike other dormant animals,the frogs appeared to decrease rates of proton leak to a greater extent than ATP synthesis, consistent with an increase in mitochondrial coupling efficiency. The significant energy savings observed at the mitochondrial level were reflected at higher levels of biological organisation, with tissue oxygen consumption depressed by as much as 81% and whole animal metabolic rate by 82%. Cyclorana alboguttata can survive in a dormant state for several years and we propose the hypothesis that energy efficiency is increased during aestivation.
Publisher: Elsevier BV
Date: 09-2011
DOI: 10.1016/J.CBPA.2011.05.015
Abstract: In 1960, C.G. Wilber in a laboratory-based study described for the first time the changes in heart rate with submergence in the American alligator noting in particular the marked bradycardia that occurred during forced es. This short review summarizes the major advances in our understanding of ing and the responses and role of the cardiovascular system of crocodilians during submergence in the 50 years since Wilber published his findings. These advances are attributable in part to the technological advances made in physiological monitoring devices and wildlife telemetry that have not only provided greater elucidation of the hemodynamics of the unique crocodilian cardiovascular system but also allowed the natural ing behaviors and heart rates in free-ranging crocodiles to be recorded. Of note, telemetric field-based studies have revealed that wild free-ranging crocodiles typically undertake only short es, less than 20 min, yet crocodiles are also capable of es of many hours in duration. In contrast to Wilber's study, es recorded from free-ranging crocodiles were found to be accompanied by only a modest bradycardia, highlighting the often confounding effects associated with captive animals monitored under laboratory conditions. More recent studies have also documented the complex central flow and pressure patterns of crocodilians, including a pulmonary to systemic shunt that can be initiated by a unique intracardiac valve located in the subpulmonary conus. The role and significance of this cardiac shunt remains controversial and the focus of recent lab-based studies. We contend that elucidation of the role and significance of the cardiac shunt in crocodilians will only be achieved by monitoring telemetrically the central cardiovascular flows and pressures in non-captive animals that are undisturbed and free-ranging. This presents the challenge ahead in the next 50 years.
Publisher: The Company of Biologists
Date: 2022
DOI: 10.1242/JEB.243885
Publisher: The Company of Biologists
Date: 2020
DOI: 10.1242/JEB.224444
Abstract: Rising temperatures are set to imperil freshwater fishes as climate change ensues unless compensatory strategies are employed. However, the presence of additional stressors, such as elevated nitrate concentrations, may affect the efficacy of compensatory responses. Here, juvenile silver perch (Bidyanus bidyanus) were exposed to current-day summer temperatures (28oC) or a future climate-warming scenario (32oC) and simultaneously exposed to one of three ecologically relevant nitrate concentrations (0, 50 or 100 mg L−1). We measured indicators of fish performance (growth, swimming), aerobic scope (AS) and upper thermal tolerance (CTMAX) to test the hypothesis that nitrate exposure would increase susceptibility to elevated temperatures and limit thermal compensatory responses. After 8 weeks of acclimation, the thermal sensitivity and plasticity of AS and swimming performance were tested at three test temperatures (28, 32, 36oC). The AS of 28oC-acclimated fish declined with increasing temperature, and the effect was more pronounced in nitrate exposed in iduals. In these fish, declines in AS corresponded with poorer swimming performance and a 0.8oC decrease in CTMAX compared to unexposed fish. In contrast, acclimation to 32oC masked the effects of nitrate fish acclimated to 32oC displayed a thermally insensitive phenotype whereby locomotor performance remained unchanged, AS was maintained and CTMAX was increased by ∼1oC irrespective of nitrate treatment compared to fish acclimated to 28oC. Growth was however markedly reduced in 32oC-acclimated compared to 28oC-acclimated fish. Our results indicate that nitrate exposure increases the susceptibility of fish to acute high temperatures, but thermal compensation can override some of these potential detrimental effects.
Publisher: Wiley
Date: 29-08-2017
DOI: 10.1111/DDI.12618
Publisher: Oxford University Press (OUP)
Date: 21-04-2014
Publisher: Elsevier BV
Date: 03-1994
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/ZO02036
Abstract: Semi-aquatic animals represent a transitional locomotor condition characterised by the possession of morphological features that allow locomotion both in water and on land. Most ecologically important behaviours of crocodilians occur in the water, raising the question of whether their 'terrestrial construction' constrains aquatic locomotion. Moreover, the demands for aquatic locomotion change with life-history stage. It was the aim of this research to determine the kinematic characteristics and efficiency of aquatic locomotion in different-sized crocodiles (Crocodylus porosus). Aquatic propulsion was achieved primarily by tail undulations, and the use of limbs during swimming was observed only in very small animals or at low swimming velocities in larger animals. Over the range of swimming speeds we examined, tail beat litude did not change with increasing velocity, but litude increased significantly with body length. However, litude expressed relative to body length decreased with increasing body length. Tail beat frequency increased with swimming velocity but there were no differences in frequency between different-sized animals. Mechanical power generated during swimming and thrust increased non-linearly with swimming velocity, but disproportionally so that kinematic efficiency decreased with increasing swimming velocity. The importance of unsteady forces, expressed as the reduced frequency, increased with increasing swimming velocity. Amplitude is the main determinant of body-size-related increases in swimming velocity but, compared with aquatic mammals and fish, crocodiles are slow swimmers probably because of constraints imposed by muscle performance and unsteady forces opposing forward movement. Nonetheless, the kinematic efficiency of aquatic locomotion in crocodiles is comparable to that of fully aquatic mammals, and it is considerably greater than that of semi-aquatic mammals.
Publisher: Elsevier BV
Date: 05-2006
DOI: 10.1016/J.YGCEN.2005.07.007
Abstract: This study examined the effect of transfer to increased environmental salinity on the circulating levels of angiotensin II (ANG II), C-type natriuretic peptide (CNP), and arginine vasotocin (AVT) in the euryhaline elasmobranch, Carcharhinus leucas. Plasma levels of ANG II and CNP were significantly increased in C. leucas chronically acclimated to seawater (SW) in comparison to freshwater (FW) acclimated fish. There was no difference in plasma AVT levels. Acute transfer of FW fish to 75% SW induced an increase in plasma ANG II levels within 12 h, and subsequent transfer from 75 to 100% SW further increased plasma ANG II levels at both 24 and 72 h. No change in plasma CNP was observed during acute transfer to increased salinity. However, a significant increase in plasma AVT levels was observed following 96 h in 75% SW and 24 h in 100% SW. In chronically SW acclimated C. leucas plasma osmolality, sodium, chloride, and urea were all significantly higher than FW acclimated fish but there was no difference in haematocrit. Acute transfer of C. leucas to 75% SW induced a significant increase in plasma osmolality, sodium and urea concentrations within 96 h of transfer. Subsequent transfer from 75 to 100% SW induced a further increase in these variables within 24 h in addition to a significant increase in plasma chloride above control levels. Haematocrit did not differ between the experimental and control groups throughout the acute study. Circulating levels of ANG II were significantly correlated to plasma, sodium, chloride, and urea concentrations during acclimation to SW. Conversely, circulating levels of CNP and AVT did not correlate to plasma osmolytes, however, CNP was significantly correlated to haematocrit during acclimation to seawater.
Publisher: Wiley
Date: 2005
DOI: 10.1002/JEZ.A.199
Abstract: Plasma urea levels and hepatic urea production in the euryhaline bull shark, Carcharhinus leucas, acclimated to freshwater and seawater environments were measured. It was found that plasma urea concentration increased with salinity and that this increase was, in part, the result of a significant increase in hepatic production of urea. This study provides direct evidence that hepatic production of urea plays an important role in the osmoregulatory strategy of C. leucas.
Publisher: Cold Spring Harbor Laboratory
Date: 19-04-2022
DOI: 10.1101/2022.04.18.488693
Abstract: Many aquatically respiring animals inhabiting low pH waters can suffer acute inhibition of ion uptake and loss of branchial (gill) epithelial integrity, culminating in a fatal, rapid loss of body Na + . Environmental calcium levels ([Ca 2+ ] e ) are pivotal in maintaining branchial junction integrity, with supplemental Ca 2+ reversing the negative effects of low pH in some animals. Tolerance of some naturally acidic environments by aquatic animals is further complicated by low [Ca 2+ ] e , yet many of these environments are surprisingly bio erse. How these animals overcome the combined damaging actions of low pH and low environmental Ca 2+ remains unknown. Here, we examined the effects of [Ca 2+ ] e on the response to low pH in larvae of the highly acid tolerant frog Limnodynastes terraereginae . Acute exposure to low pH water in the presence of low [Ca 2+ ] e increased net Na + efflux. Provision of additional [Ca 2+ ] e reduced net Na + efflux, but the effect was saturable. Acclimation to both low and high [Ca 2+ ] e improved the resistance of larvae to Na + efflux at low pH. Inhibition of apical Ca 2+ uptake by ruthenium red resulted in an abrupt loss of tolerance to low pH in larvae acclimated to low pH water. Acclimation to acidic water increased branchial gene expression of the intracellular Ca 2+ transport protein calbindin, consistent with a role for increased transcellular Ca 2+ trafficking in the tolerance of acidic water. This study confirmed the physiological challenge of low [Ca 2+ ] e on branchial integrity in acidic waters and highlighted a potential role for maintenance of transcellular Ca 2+ uptake in the acid tolerance of L. terraereginae . Tolerance of naturally acidic, dilute, and soft waters by larvae of the frog Limnodynastes terraereginae involves adaptations to the branchial calcium transport pathway which protects intercellular junctions against damage.
Publisher: Elsevier BV
Date: 07-2018
DOI: 10.1016/J.AQUATOX.2018.05.004
Abstract: Multiple environmental stressors, including nutrient effluents (i.e. nitrates [NO
Publisher: University of Chicago Press
Date: 05-2008
DOI: 10.1086/528779
Abstract: Locomotion is a common measure of performance used in studies of thermal acclimation because of its correlation with predator escape and prey capture. However, for sedentary animals such as freshwater turtles, we propose that ing behavior may be a more ecologically relevant measure of performance. Increasing e duration in hatchling turtles reduces predator exposure and therefore functions as an ecological benefit. Diving behavior is thermally dependent, and in some species of freshwater turtles, it is also reliant on aquatic respiration. This study examined the influence of thermal acclimation on ing behavior, aquatic respiration, and locomotor performance in the endangered, bimodally respiring Mary River turtle Elusor macrurus. Diving behavior was found to partially acclimate at 17 degrees C, with turtles acclimated to a cold temperature (17 degrees C) having a significantly longer e duration than hatchlings acclimated to a warm temperature (28 degrees C). This increase in e duration at 17 degrees C was not a result of physiological alterations in metabolic rate but was due instead to an increase in aquatic oxygen consumption. Increasing aquatic oxygen consumption permitted cold-acclimated hatchlings to remain submerged for significantly longer periods, with one turtle undertaking a e of over 2.5 d. When burst-swimming speed was used as the measure of performance, thermal acclimation was not detected. Overall, E. macrurus demonstrated a partial ability to acclimate to changes in environmental temperature.
Publisher: Springer Science and Business Media LLC
Date: 07-05-2001
Abstract: The foramen of Panizza is located within the outflow tract of the crocodilian heart, between the left and right aortas. It has been suggested that the foramen of Panizza has a variable calibre, which could explain the profound changes in the distribution of flows and pressure profiles recorded in the right and left aortas. We investigated this possibility using a modified in-situ perfused heart preparation in combination with isolated strip preparations from the outflow tract. In the perfused heart preparation, bolus injections of adrenaline increased the resistance in the foramen of Panizza, indicating a decrease in its diameter. Isolated strip preparations from the outflow tract showed a concentration-dependent increase in tension in response to adrenaline, while vasoactive intestinal polypeptide caused a relaxation in adrenaline pre-contracted strip preparations. We propose that an increase in the diameter of the foramen of Panizza may be important during pulmonary to systemic shunts to allow blood to flow from the left to right aorta (reverse foramen flow) in order to supply the carotid and coronary arteries. During non-shunting conditions, a constricted foramen may prevent excess flow from the right to left aorta during diastole.
Publisher: Wiley
Date: 03-06-2019
DOI: 10.1111/COBI.13328
Abstract: The optimal design of reserve networks and fisheries closures depends on species occurrence information and knowledge of how anthropogenic impacts interact with the species concerned. However, challenges in surveying mobile and cryptic species over adequate spatial and temporal scales can mask the importance of particular habitats, leading to uncertainty about which areas to protect to optimize conservation efforts. We investigated how telemetry-derived locations can help guide the scale and timing of fisheries closures with the aim of reducing threatened species bycatch. Forty juvenile speartooth sharks (Glyphis glyphis) were monitored over 22 months with implanted acoustic transmitters and an array of hydrophone receivers. Using the decision-support tool Marxan, we formulated a permanent fisheries closure that prioritized areas used more frequently by tagged sharks and considered areas perceived as having high value to fisheries. To explore how the size of the permanent closure compared with an alternative set of time-area closures (i.e., where different areas were closed to fishing at different times of year), we used a cluster analysis to group months that had similar arrangements of selected planning units (informed by shark movements during that month) into 2 time-area closures. Sharks were consistent in their timing and direction of migratory movements, but the number of tagged sharks made a big difference in the placement of the permanent closure 30 in iduals were needed to capture behavioral heterogeneity. The dry-season (May-January) and wet-season (February-April) time-area closures opened 20% and 25% more planning units to fishing, respectively, compared with the permanent closure with boundaries fixed in space and time. Our results show that telemetry has the potential to inform and improve spatial management of mobile species and that the temporal component of tracking data can be incorporated into prioritizations to reduce possible impacts of spatial closures on established fisheries.
Publisher: The Company of Biologists
Date: 05-2018
DOI: 10.1242/JEB.167445
Abstract: Batrachochytrium dendrobatidis (Bd) is a pathogenic fungus that causes the cutaneous, infectious disease chytridiomycosis and has been implicated in population declines of numerous anuran species worldwide. Proximate cause of death by chytridiomycosis is asystolic cardiac arrest as a consequence of severe disruption to electrolyte balance. Animals heavily infected with Bd also experience a disruption to their skin sloughing regime, indicating that core functions of the skin, such as water retention, may be severely impacted. This study examined how skin sloughing, body size and Bd infection interact to influence water loss rates in five Australian frog species: Litoria caerulea, Limnodynastes peronii, Lechriodus fletcheri, Limnodynastes tasmaniensis and Platyplectrum ornatum. Rates of water loss more than doubled during sloughing in L. caerulea. During active periods across all species, water loss rates were on average 232% higher in Bd infected frogs than in uninfected frogs. This indicates that dehydration stress may be a significant factor contributing to the morbidity of severely Bd infected anurans, a symptom that is then exacerbated by an increased rate of sloughing. When taking size into account, smaller and/or juvenile anurans may be more at risk from dehydration due to Bd infection, as they lose a greater amount of water and slough more frequently than adults. This may in part explain the higher mortality rates typical for small and juvenile frogs infected with Bd. Understanding how Bd affects the core functions of the skin, including rates of water loss, can improve our predictions of disease outcome in hibians.
Publisher: Elsevier BV
Date: 05-2001
Publisher: The Company of Biologists
Date: 05-2011
DOI: 10.1242/JEB.053124
Abstract: Understanding the mechanisms that constrain the invasiveness of introduced animals is essential for managing invasions and for predicting their limits. In most vertebrate species, the capacity for invasion relies upon the physiological systems that support locomotion, and oxygen transport and metabolism may become limiting as environmental temperatures increase as predicted by the oxygen limitation hypothesis. Here we test the oxygen limitation hypothesis and propose the alternative hypothesis that within-in idual plasticity will compensate for thermal variation. We show that during exercise in the invasive cane toad (Rhinella marina) oxygen transport by the cardiovascular system was maximised in warm-acclimated toads at high (30°C) temperatures, and that oxygen content of arterial blood was not affected by temperature. Resting oxygen consumption remained stable across a 10°C temperature range (20–30°C) when toads were allowed to acclimate, so that there was no increase in resting oxygen demand that could lead to a decrease in aerobic scope at high temperatures. Additionally, temperature acclimation had no effect on arterial–venous differences in oxygen partial pressures. Toads relied more on glycolytic ATP production at low temperatures to support locomotor activity. Mitochondrial capacities (citrate synthase and cytochrome c oxidase activities) were greatest at warmer temperatures. Interestingly, the metabolic cost of exercise increased at low temperatures. In contradiction to predictions by the oxygen limitation hypothesis, aerobic performance was not limited by high temperatures. On the contrary, the relatively slow advance of cane toads to cooler climates can be explained by the constraints of low temperatures on the physiological systems supporting locomotion. It is likely that human-induced global warming will facilitate invasions of environments that are currently too cool to support cane toads.
Publisher: Elsevier BV
Date: 05-1991
Publisher: Wiley
Date: 20-09-2013
DOI: 10.1002/JMOR.20080
Abstract: Animals that undergo prolonged dormancy experience minimal muscle disuse atrophy (MDA) compared to animals subjected to artificial immobilisation over shorter timeframes. An association between oxidative stress and MDA suggests that metabolic depression presumably affords dormant animals some protection against muscle disuse. Because aerobic metabolism is temperature sensitive, we proposed that MDA in dormant (aestivating) ectotherms would be enhanced at elevated temperatures. In the green-striped burrowing frog, Cyclorana alboguttata, the thermal sensitivity of skeletal muscle metabolic rate is muscle-specific. We proposed that the degree of atrophy experienced during aestivation would correlate with the thermal sensitivity of muscle metabolic rate such that muscles with a relatively high metabolic rate at high temperatures would experience more disuse atrophy. To test this hypothesis, we examined the effect of temperature and aestivation on the extent of MDA in two functionally different muscles: the M. gastrocnemius (jumping muscle) and M. iliofibularis (non-jumping muscle), in C. alboguttata aestivating at 24 or 30 °C for 6 months. We compared a range of morphological parameters from muscle cross-sections stained with succinic dehydrogenase to show that muscle-specific patterns of disuse atrophy were consistent with the relative rates of oxygen consumption of those muscle types. However, despite muscle-specific differences in thermal sensitivity of metabolic rate, aestivation temperature did not influence the extent of atrophy in either muscle. Our results suggest that the muscles of frogs aestivating at high temperatures are defended against additional atrophy ensuring protection of muscle function during long periods of immobilisation.
Publisher: The Company of Biologists
Date: 2018
DOI: 10.1242/JEB.191817
Abstract: Chytridiomycosis, a lethal fungal skin disease of hibians, fatally disrupts ionic and osmotic homeostasis. Infected hibians increase their skin shedding rate (sloughing) to slow pathogen growth, but the sloughing process also increases skin permeability. Healthy hibians increase active ion uptake during sloughing by increasing ion transporter abundance to offset the increased skin permeability. How chytridiomycosis affects the skin function during and between sloughing events remains unknown. Here we show that non-sloughing frogs with chytridiomycosis have impaired cutaneous sodium uptake, in part because they have fewer sodium transporters in their skin. Interestingly, sloughing was associated with a transient increase in sodium transporter activity and abundance, suggesting that the newly exposed skin layer is initially fully functional until the recolonization of the skin by the fungus again impedes cutaneous function. However, the temporary restoration of skin function during sloughing does not restore ionic homeostasis, and the underlying loss of ion uptake capacity is ultimately detrimental for hibians with chytridiomycosis.
Publisher: Elsevier BV
Date: 06-2009
Publisher: Springer Science and Business Media LLC
Date: 05-2004
DOI: 10.1007/S00360-004-0420-X
Abstract: Changes in blood-gas, acid-base, and plasma-ion status were investigated in the bimodally respiring turtle, Rheodytes leukops, during prolonged es of up to 12 h. Given that R. leukops routinely submerges for several hours, the objective of this study was to determine whether voluntarily ing turtles remain aerobic and simultaneously avoid hypercapnic conditions over increasing e lengths. Blood PO(2), PCO(2), and pH, as well as plasma concentrations of lactate, glucose, Na(+), K(+), Cl(-), total Ca, and total Mg were determined in venous blood collected from the occipital sinus. Blood PO(2) declined significantly with e length however, oxy-haemoglobin saturation remained greater than 30% for all R. leukops s led. No changes were observed in blood PCO(2), pH, [HCO(3)(-)], or plasma glucose, with increasing e length. Despite repeated es lasting more than 2 h, plasma lactate remained less than 3 mmol l(-1) for all R. leukops s led, indicating the absence of anaerobiosis. Compensatory acid-base adjustments associated with anaerobiosis (e.g. declining [Cl(-)], increasing total [Ca] and [Mg]) were likewise absent, with plasma-ion concentrations remaining stable with increasing e length. Results indicate that R. leukops utilises aquatic respiration to remain aerobic during prolonged es, thus effectively avoiding the development of a metabolic and respiratory acidosis.
Publisher: The Company of Biologists
Date: 2020
DOI: 10.1242/JEB.228379
Abstract: Glycogen is a critical store for locomotion. Depleted glycogen stores are associated with increased fatigue during exercise. The reduced effectiveness of low-carbohydrate diets for weight loss over longer time periods may arise because such diets reduce glycogen stores and thereby physical activity energy expenditure. To explore the effect of a low-carbohydrate diet on activity and glycogen utilisation, we fed adult Drosophila melanogaster a standard or low-carbohydrate diet for nine days and measured patterns of flight activity and rates of glycogen depletion. We hypothesised that flight activity and rates of glycogen depletion would be reduced on a low-carbohydrate diet. Flight activity was elevated in the low-carbohydrate group but glycogen depletion rates were unchanged. We conclude that increased activity is likely a foraging response to carbohydrate deficiency and speculate that the previously demonstrated metabolic depression that occurs on a low-carbohydrate diet in this species may allow for increased flight activity without increased glycogen depletion.
Publisher: Cold Spring Harbor Laboratory
Date: 02-12-2019
DOI: 10.1101/861898
Abstract: Freshwater ecosystems have been severely fragmented by artificial in-stream structures designed to manage water for human use. Significant efforts have been made to reconnect freshwater systems for fish movement, through the design and installation of dedicated fish passage structures (fishways) and by incorporating fish-sensitive design features into conventional infrastructure (e.g. culverts). Key to the success of these structures is making sure that the water velocities within them do not exceed the swimming capacities of the local fish species. Swimming performance data is scarce for Australian fish, which have a reduced swimming capacity when compared to many North American and European species. To help close this knowledge gap and assist fisheries management and civil engineering, we report the swimming performance capacities of twenty-one small-bodied fish and juveniles ( 10 cm) of large bodied species native to Australia as measured by critical swimming speed ( U crit) and burst swimming speed ( U sprint) in a recirculating flume. This data is complemented by endurance swim trials in a 12-meter hydraulic flume channel, and by measures of flume traverse success. Building on the utility of this dataset, we used a panel of morphological, behavioural and ecological traits to first assess their relative contributions to the observed swimming performance data, and second, to determine if they could be used to predict swimming performance capacity – a useful tool to assist in the management of species of conservation concern where access to swimming performance data may be limited. We found that body length combined with depth station (benthic, pelagic or surface) explained most of the interspecific variation in observed swimming performance data, followed by body shape and tail shape. These three traits were the most effective at predicting swimming performance in a model/unknown fish. This data will assist civil engineers and fisheries managers in Australia to mitigate the impact of in-stream structures on local fish populations.
Publisher: Springer Science and Business Media LLC
Date: 13-03-2019
DOI: 10.1007/S00442-019-04382-4
Abstract: Body size and age are crucial factors influencing reproductive capacity and success. As females grow, their reproductive investment and success often increase due to improved overall physiological condition and experience gained through successive reproductive events. While much of this work has been conducted on birds and mammals, surprisingly little is known on how body size affects nesting decisions in other long-lived vertebrates. We monitored the movements and nesting behaviour of 57 wild female estuarine crocodiles Crocodylus porosus over a 10-year period (and across consecutive nesting seasons) using externally mounted satellite tags, implanted acoustic transmitters and a network of submerged acoustic receivers. Applying Hidden Markov models to the telemetry-derived location data revealed that female nesting behaviours could be split into three distinct states: (i) ranging movements within home ranges and at nesting sites (ii) migrations to and from nesting sites (iii) and nesting/nest guarding. We found that during migration events, larger females migrated further and remained away from dry season territories for longer periods than smaller in iduals. Furthermore, not only were migratory movements stimulated by increases in rainfall, larger females migrated to nest sites at lower rainfall thresholds than smaller females. We provide some of the first evidence of body size influencing nesting decisions in an ectothermic vertebrate, with shifts likely resulting from an increased willingness to invest in nest protection among larger and more experienced females.
Publisher: Cold Spring Harbor Laboratory
Date: 23-12-2021
DOI: 10.1101/2021.12.21.473748
Abstract: Determining the contribution of elevated ultraviolet-B radiation (UVBR 280 – 315 nm) to hibian population declines is being hindered by a lack of knowledge about how different acute UVBR exposure regimes during early life history stages might affect post-metamorphic stages via long-term carryover effects. We acutely exposed tadpoles of the Australian green tree frog ( Litoria caerulea ) to a combination of different UVBR irradiances and doses in a multi-factorial experiment, and then reared them to metamorphosis in the absence of UVBR to assess carryover effects in subsequent juvenile frogs. Dose and irradiance of acute UVBR exposure influenced carryover effects into metamorphosis in somewhat opposing manners. Higher doses of UVBR exposure in larvae yielded improved rates of metamorphosis. However, exposure at a high irradiance resulted in frogs metamorphosing smaller in size and in poorer condition than frogs exposed to low and medium irradiance UVBR as larvae. We also demonstrate some of the first empirical evidence of UVBR-induced telomere shortening in vivo , which is one possible mechanism for life-history trade-offs impacting condition post-metamorphosis. These findings contribute to our understanding of how acute UVBR exposure regimes in early life affect later life-history stages, which has implications for how this stressor may shape population dynamics. We demonstrate physiological carryover effects in hibians that link larval UV exposure to detrimental impacts on juvenile frogs, including telomere shortening, which has implications for how UV shapes hibian populations.
Publisher: The Company of Biologists
Date: 09-2016
DOI: 10.1242/JEB.128348
Abstract: Bone mass and skeletal muscle mass are controlled by factors such as genetics, diet and nutrition, growth factors and mechanical stimuli. Whereas increased mechanical loading of the musculoskeletal system stimulates an increase in the mass and strength of skeletal muscle and bone, reduced mechanical loading and disuse rapidly promote a decrease in musculoskeletal mass, strength and ultimately performance (i.e. muscle atrophy and osteoporosis). In stark contrast to artificially immobilised laboratory mammals, animals that experience natural, prolonged bouts of disuse and reduced mechanical loading, such as hibernating mammals and aestivating frogs, consistently exhibit limited or no change in musculoskeletal performance. What factors modulate skeletal muscle and bone mass, and what physiological and molecular mechanisms protect against losses of muscle and bone during dormancy and following arousal? Understanding the events that occur in different organisms that undergo natural periods of prolonged disuse and suffer negligible musculoskeletal deterioration could not only reveal novel regulatory factors but also might lead to new therapeutic options. Here, we review recent work from a erse array of species that has revealed novel information regarding physiological and molecular mechanisms that dormant animals may use to conserve musculoskeletal mass despite prolonged inactivity. By highlighting some of the differences and similarities in musculoskeletal biology between vertebrates that experience disparate modes of dormancy, it is hoped that this Review will stimulate new insights and ideas for future studies regarding the regulation of atrophy and osteoporosis in both natural and clinical models of muscle and bone disuse.
Publisher: Springer Science and Business Media LLC
Date: 04-05-2011
DOI: 10.1007/S00360-011-0581-3
Abstract: Recent catastrophic global hibian declines have been partially linked to increases in UV-B radiation as a consequence of stratospheric ozone depletion. Previous studies have shown that in the presence of other environmental stressors including aquatic pH and temperature and the presence of contaminants or pathogens, the lethal effects of UV-B on hibian larvae are enhanced due to interactions between the stressors. Little is known about the interactions between UV-B and aquatic hypoxia, a common and significant natural stressor of hibian larvae. We examined the potential effects of UV-B and aquatic hypoxia in combination on embryonic survival, developmental rate, body mass and locomotor performance of embryos and larvae of the striped marsh frog, Limnodynastes peronii. We found that while both UV-B and hypoxia independently had substantial negative effects on the developing embryos of L. peronii, they did not interact in a multiplicative or antagonistic manner. The effects of the stressors in combination were as might be predicted based on the knowledge of their independent actions alone (i.e. an additive effect). In all cases developing embryos exposed to both UV-B and hypoxia were more severely affected than those exposed to either UV-B or hypoxia alone. The results of this study show the importance of examining both the direct actions of in idual stressors and how these may be influenced by the presence of other environmental factors.
Publisher: Springer Science and Business Media LLC
Date: 18-03-2019
DOI: 10.1038/S41559-019-0839-9
Abstract: Organisms vary widely in size, from microbes weighing 0.1 pg to trees weighing thousands of megagrams - a 10
Publisher: Elsevier BV
Date: 05-2023
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/MF08153
Abstract: Crocodilians are by their very nature difficult animals to study. However, research on wild animals is essential for the development of reliable long-term management. Here, we describe methods for the acquisition and monitoring of behavioural and physiological variables from free-ranging crocodilians through the use of archival tags (data-loggers) and via satellite, radio and acoustic telemetry. Specifically, the attachment or implantation of electronic tags is described and ex les provided of the type of data that can be collected. Our research group has used a combination of approaches to monitor the movements, ing activity, body temperatures and heart rates of crocodilians, including studies on the Australian freshwater crocodile (Crocodylus johnstoni), the estuarine crocodile (Crocodylus porosus) and the caiman (Caiman latirostris). Each approach or method presents unique challenges and problems, chiefly as a consequence of differences in body morphology and size of the crocodilian species, their behaviours and the habitats they occupy.
Publisher: Elsevier BV
Date: 07-2009
Publisher: Wiley
Date: 26-07-2012
DOI: 10.1111/J.1523-1739.2012.01906.X
Abstract: Global increases in ultraviolet‐B radiation (UVBR) associated with stratospheric ozone depletion are potentially contributing to the decline of numerous hibian species around the world. Exposure to UVBR alone reduces survival and induces a range of sublethal effects in embryonic and larval hibians. When additional environmental stressors are present, UVBR can have compounding negative effects. Thus, examination of the effects of UVBR in the absence of other stressors may substantially underestimate its potential to affect hibians in natural habitats. We examined the independent and interactive effects of increased UVBR and high conspecific density would have embryonic and larval striped marsh frogs ( Limnodynastes peronii ). We exposed in iduals to a factorial combination of low and high UVBR levels and low, medium, and high densities of striped marsh frog tadpoles. The response variables were time to hatching, hatching success, posthatch survival, burst‐swimming performance of tadpoles (maximum instantaneous swim speed following an escape response), and size and morphology of tadpoles. Consistent with results of previous studies, we found that exposure to UVBR alone increased the time to hatching of embryos and reduced the burst‐swimming performance and size of tadpoles. Similarly, increasing conspecific density increased the time to hatching of embryos and reduced the size of tadpoles, but had no effect on burst‐swimming performance. The negative effect of UVBR on tadpole size was not apparent at high densities of tadpoles. This result suggests that tadpoles living at higher densities may invest relatively less energy in growth and thus have more energy to repair UVBR‐induced damage. Lower densities of conspecifics increased the negative effects of UVBR on developing hibians. Thus, low‐density populations, which may include declining populations, may be particularly susceptible to the detrimental effects of increased UVBR and thus may be driven toward extinction faster than might be expected on the basis of results from single‐factor studies . Relaciones entre la Densidad Conespecífica y los Efectos de la Radiación Ultravioleta‐B sobre el Tamaño de Renacuajos de Limnodynastes peronei
Publisher: Wiley
Date: 2009
DOI: 10.1111/J.1095-8649.2008.02110.X
Abstract: Muscle morphology was investigated in newly hatched barramundi Lates calcarifer larvae incubated at set temperatures (26, 29 and 31 degrees C) prior to hatching. Three days after hatching (the start of exogenous feeding), larvae from the 26 and 31 degrees C treatments were each ided into two groups and reared at that temperature or transferred over the period of several hours to 29 degrees C (control temperature). Incubation temperature significantly affected muscle cellularity in the developing embryo, with larvae incubated at 26 degrees C (mean +/-s.e. 223.3 +/- 7.9) having on average 14.4% more inner muscle fibres than those incubated at 31 degrees C (195.2 +/- 8.8) and 4.8% more than those incubated at 29 degrees C (213.5 +/- 4.7). Conversely, inner muscle fibre cross-sectional area significantly increased at the warm incubation temperature in L. calcarifer, so that the total cross-sectional muscle area was not different between treatment groups. The total cross-sectional area of superficial muscle fibres and the proportion of superficial to total fibre cross-sectional area in just hatched L. calcarifer were also affected by incubation temperature, with incubation at the cool temperature (26 degrees C) increasing both the total cross-sectional area and proportion of superficial muscle fibres. By 9 days post-hatch, the aforementioned differences were no longer significant. Similarly, there was no difference in total superficial fibre cross-sectional area between any treatment groups of L. calcarifer, whereas incubation temperature still significantly affected the proportion of superficial to total muscle fibre cross-sectional area. Larvae hatched and grown at 31 degrees C had a significantly reduced percentage of superficial muscle cross-sectional area (mean +/-s.e. 5.11 +/- 0.66%) compared with those incubated and grown at 29 degrees C (8.04 +/- 0.77%) and 26 degrees C (9.32 +/- 0.56%) and those incubated at 26 degrees C and transferred to 29 degrees C (7.52 +/- 0.53%), and incubated at 31 degrees C and transferred to 29 degrees C (6.28 +/- 0.69%). These results indicate that changes in muscle cellularity induced by raising or lowering the incubation temperature of L. calcarifer display varying degrees of persistence over developmental time. The significance of these findings to the culture of L. calcarifer is discussed.
Publisher: Elsevier BV
Date: 05-1997
DOI: 10.1016/S0300-9629(96)00283-6
Abstract: We examined the possibility that the heart of the tuttle Chrysemys scripta is an exceptional anaerobic performer, by measuring myocardial power output, lactate output, and estimated ATP turnover in perfused heart preparations. Over a range of myocardial power outputs at 5 and 15 degrees C we find that turtle hearts perfused with anoxic saline do not show a particularly outstanding ability to produce ATP anaerobically. Furthermore, at 15 degrees C anoxia reduced the ATP turnover rate to 50% of the normoxic rate. At 5 degrees C the anoxia-induced depression of ATP turnover was even more pronounced, being 4-fold lower than the normoxic rate. In addition, anoxia at 5 degrees C reduced the basal metabolic rate of the tuttle heart. We conclude that long-term cardiac tolerance of hypoxia in this species is more likely related to metabolic depression rather than to an exceptional anaerobic performance.
Publisher: Wiley
Date: 09-10-2020
DOI: 10.1111/GCB.14837
Abstract: Ultraviolet B radiation (UVBR) damages the DNA of exposed cells, causing dimers to form between adjacent pyrimidine nucleotides. These dimers block DNA replication, causing mutations and apoptosis. Most organisms utilize biochemical or biophysical DNA repair strategies to restore DNA structure however, as with most biological reactions, these processes are likely to be thermally sensitive. Tadpoles exposed to elevated UVBR at low environmental temperatures have significantly higher rates of mortality and developmental deformities compared with tadpoles exposed to the same levels of UVBR at higher environmental temperatures. We hypothesized that low environmental temperatures impair the primary enzymatic (photolyase) DNA repair pathway in hibians, leading to the accumulation of DNA damage. To test this hypothesis, we compared DNA repair rates and photolyase gene expression patterns in Limnodynastes peronii . Tadpoles were acutely exposed to UVBR for 1 hr at either 20 or 30°C, and we measured DNA damage and photolyase expression levels at intervals following this exposure. Temperature had a significant effect on the rate of DNA repair, with repair at 30°C occurring twice as fast as repair at 20°C. Photolyase gene expression (6‐4 PP and CPD) was significantly upregulated by UVBR exposure, with expression levels increasing within 6 hr of UVBR exposure. CPD expression levels were not significantly affected by temperature, but 6‐4 PP expression was significantly higher in tadpoles in the 30°C treatment within 12 hr of UVBR exposure. These data support the hypothesis that DNA repair rates are thermally sensitive in tadpoles and may explain why enigmatic hibian declines are higher in montane regions where UVBR levels are naturally elevated and environmental temperatures are lower.
Publisher: Elsevier BV
Date: 2016
Publisher: Elsevier BV
Date: 1988
DOI: 10.1016/0742-8413(88)90155-7
Abstract: 1. The behaviour of American cockroaches envenomated with Latrodectus katipo venom was correlated with neurophysiological events recorded from an isolated cockroach CNS preparation to which venom was applied. 2. The injection of a venom extract into cockroaches caused convulsions (3 behavioural categories: quivering, jerking and hyperextension) which eventually led to paralysis and death. 3. Changes in the spontaneous activity of nerve 5 (from the metathoracic ganglion) corresponded to the time course of envenomation behaviours. An initial increase in discharge peaked 5-10 min after application and subsequently decreased to become irreversibly blocked.
Publisher: Elsevier BV
Date: 04-2006
Publisher: The Company of Biologists
Date: 15-02-2017
DOI: 10.1242/JEB.151019
Abstract: Ultraviolet B radiation (UV-B) is an important environmental driver that can affect locomotor performance negatively by inducing production of reactive oxygen species (ROS). Prolonged regular exercise increases antioxidant activities, which may alleviate the negative effects of UV-B-induced ROS. Animals naturally performing exercise, such as humans performing regular exercise or fish living in flowing water, may therefore be more resilient to the negative effects of UV-B. We tested this hypothesis in a fully factorial experiment, where we exposed mosquitofish (Gambusia holbrooki) to UV-B and control (no UV-B) conditions in flowing and still water. We show that fish exposed to UV-B and kept in flowing water had increased sustained swimming performance (Ucrit), increased antioxidant defences (catalase activity and glutathione concentrations) and reduced cellular damage (lipid peroxidation and protein carbonyl concentrations) compared with fish in still water. There was no effect of UV-B or water flow on resting or maximal rates of oxygen consumption. Our results show that environmental water flow can alleviate the negative effects of UV-B-induced ROS by increasing defence mechanisms. The resultant reduction in ROS-induced damage may contribute to maintain locomotor performance. Hence, the benefits of regular exercise are ‘transferred’ to improve resilience to the negative impacts of UV-B. Ecologically, the mechanistic link between responses to different habitat characteristics can determine the success of animals. These dynamics have important ecological connotations when river or stream flow changes as a result of weather patterns, climate or human modifications.
Publisher: The Company of Biologists
Date: 2014
DOI: 10.1242/JEB.096834
Abstract: Suppression of disuse-induced muscle atrophy has been associated with altered mitochondrial reactive oxygen species (ROS) production in mammals. However, despite extended hindlimb immobility aestivating animals exhibit little skeletal muscle atrophy compared with artificially-immobilised mammalian models. Therefore, we studied mitochondrial respiration and ROS (H2O2) production in permeabilised muscle fibres of the green-striped burrowing frog, Cyclorana alboguttata. Mitochondrial respiration within saponin-permeabilised skeletal and cardiac muscle fibres was measured concurrently with ROS production using high-resolution respirometry coupled to custom-made fluorometers. After four months of aestivation, C. alboguttata had significantly depressed whole body metabolism by approximately 70% relative to control (active) frogs, and mitochondrial respiration in saponin-permeabilised skeletal muscle fibres decreased by almost 50% both in the absence of ADP and during oxidative phosphorylation. Mitochondrial ROS production showed up to an 88% depression in aestivating skeletal muscle when malate, succinate and pyruvate were present at concentrations likely reflecting those in vivo. The percentage ROS released per O2 molecule consumed was also approximately 94 % less at these concentrations indicating an intrinsic difference in ROS production capacities during aestivation. We also examined mitochondrial respiration and ROS production in permeabilised cardiac muscle fibres and found that aestivating frogs maintained respiratory flux and ROS production at control levels. These results show that aestivating C. alboguttata has the capacity to independently regulate mitochondrial function in skeletal and cardiac muscles. Furthermore, this work indicates that ROS production can be suppressed in the disused skeletal muscle of aestivating frogs, which may in turn protect against potential oxidative damage and preserve skeletal muscle structure during aestivation and following arousal.
Publisher: The Company of Biologists
Date: 2014
DOI: 10.1242/JEB.097006
Abstract: Animals may overcome the challenges of temperature instability through behavioural and physiological mechanisms in response to short and long term temperature changes. When ectotherms face the challenge of large diel temperature fluctuations one strategy may be to reduce the thermal sensitivity of key traits in order to maintain performance across the range of temperatures experienced. Additional stressors may limit the ability of animals to respond to these thermally challenging environments through changes to energy partitioning, or interactive effects. Ornate burrowing frog (Platyplectrum ornatum) tadpoles develop in shallow ephemeral pools that experience high diel thermal variability (& °C) and can be exposed to high levels of UV-B radiation. Here we investigated how development in fluctuating verses stable temperature conditions in the presence of high or low UV-B radiation influences thermal tolerance and thermal sensitivity of performance traits of P. ornatum tadpoles. Tadpoles developed in either stable (24°C) or fluctuating temperatures (18-32°C) under high or low UV-B conditions. Tadpoles were tested for upper critical thermal limits and thermal dependence of resting metabolic rate and maximum burst swimming performance. We hypothesised that developmental responses to thermal fluctuations would increase thermal tolerance and reduce thermal dependence of physiological traits, and that trade-offs in the allocation of metabolic resources towards repairing UV-B induced damage may limit the ability to maintain performance over the full range of temperatures experienced. We found that P. ornatum tadpoles were thermally insensitive for both burst swimming performance, across the range of temperatures tested, and resting metabolic rate at high temperatures independent of developmental conditions. Maintenance of performance led to trade-off for growth under fluctuating temperatures and UV-B exposure. Temperature treatment and UV-B exposure had an interactive effect on upper critical thermal limits possibly due to the up-regulation of the cellular stress response. Thermal independence of key traits may allow P. ornatum tadpoles to maintaining performance in the thermal variability inherent in their environment.
Publisher: Wiley
Date: 04-05-2021
Abstract: Climate affects all aspects of biology. Physiological traits play a key role in mediating these effects, because they define the fundamental niche of each organism. Climate change is likely to shift environmental conditions away from physiological optima. The consequences for species are significant: they must alter their physiology through plasticity or adaptation, move, or decline to extinction. The ability to understand and predict such organismal responses to global change is, however, only as good as the geographical coverage of the data on which these predictions are based. Geographical biases in the state of physiological knowledge have been identified, but it has not been determined if these geographical biases are likely to limit our capacity to predict the outcomes of global change. We show that current knowledge of physiological traits is representative of only a limited range of the climates in which terrestrial animals will be required to operate, because data for animals from only a limited range of global climates have been incorporated in existing compilations. We conclude that geographical bias in existing datasets limits our capacity to predict organismal responses in the vast areas of the planet that are unstudied, and that this geographical bias is a much greater source of uncertainty than the difference between the current climate and the projected future climate. Addressing this bias is urgent to understand where impacts will be most profound, and where the need for intervention is most pressing. A free Plain Language Summary can be found within the Supporting Information of this article.
Publisher: Springer Science and Business Media LLC
Date: 08-1993
DOI: 10.1007/BF00004374
Publisher: Elsevier BV
Date: 04-2007
Publisher: The Company of Biologists
Date: 08-2004
DOI: 10.1242/JEB.01108
Abstract: This study examines the effect of increasing water depth and water velocity upon the surfacing behaviour of the bimodally respiring turtle, Rheodytes leukops. Surfacing frequency was recorded for R. leukops at varying water depths (50, 100, 150 cm) and water velocities (5, 15, 30 cm s-1) during independent trials to provide an indirect cost-benefit analysis of aquatic versus pulmonary respiration. With increasing water velocity, R. leukops decreased its surfacing frequency twentyfold, thus suggesting a heightened reliance upon aquatic gas exchange. An elevated reliance upon aquatic respiration, which presumably translates into a decreased air-breathing frequency, may be metabolically more efficient for R. leukops compared to the expenditure (i.e. time and energy)associated with air-breathing within fast-flowing riffle zones. Additionally, R. leukops at higher water velocities preferentially selected low-velocity microhabitats, presumably to avoid the metabolic expenditure associated with high water flow. Alternatively, increasing water depth had no effect upon the surfacing frequency of R. leukops, suggesting little to no change in the respiratory partitioning of the species across treatment settings. Routinely long es (& min) recorded for R. leukopsindicate a high reliance upon aquatic O2 uptake regardless of water depth. Moreover, metabolic and temporal costs attributed to pulmonary gas exchange within a pool-like environment were likely minimal for R. leukops, irrespective of water depth.
Publisher: Wiley
Date: 26-03-2007
Publisher: Oxford University Press (OUP)
Date: 2015
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/ZO09080
Abstract: In air-breathing aquatic animals, predation is a strong selection pressure that may be reduced by modification to ing patterns. The risk of predation increases with time spent at the surface, thus shorter, more frequent surfacing events or longer, less frequent surfacing events would decrease predation risk. A reduction in time spent on the surface can be achieved by use of bimodal respiration, which is an ability to extend e duration using dissolved oxygen to supplement aerially acquired oxygen. Air is a more efficient respiratory medium however, under predation pressure, the cost of surfacing increases and the reliance on aquatic gas exchange should therefore increase. We tested whether the bimodally respiring filesnake (Acrochordus arafurae) changed its ing behaviour under simulated aerial (model bird) and aquatic (large fish) predation. Aerial predation did not alter e or surface duration, percentage time surfacing or activity. However, a greater number of longer es were observed with fewer long surface intervals, suggesting an increase in the use of aquatic gas exchange. The diel ing patterns (short night es, long day es) may provide an in-built antipredatory response to aerial predation. The threat of aquatic predation produced atypical antipredator behaviour, with longer surface intervals, shorter es and increased activity, indicating that piscivorous filesnakes may have identified the predatory fish as prey rather than a predator.
Publisher: Elsevier BV
Date: 04-2007
Publisher: Cold Spring Harbor Laboratory
Date: 27-06-2023
DOI: 10.1101/2023.06.25.546466
Abstract: 1. Increases in ultraviolet radiation (UVR) correlate spatially and temporally with global hibian population declines and interact with other stressors such as disease and temperature. Declines have largely occurred in high-altitude areas associated with greater UVR and cooler temperatures. 2. UVR is a powerful mutagenic harming organisms largely by damaging DNA. When acutely exposed to UVR at cool temperatures, hibian larvae have increased levels of DNA damage. Amphibians may be able to compensate for the depressive effects of temperature on DNA damage through thermal acclimatisation, but it is unknown whether they or other ectotherms have this capacity. 3. We reared striped marsh frog larvae ( Limnodynastes peronii ) in warm (25°C) and cool (15°C) temperatures under either a low or moderate daily dose of UVR (10 and 40 µW cm -2 UV-B for 1 h at midday, respectively) for 18-20 days and then measured immediate DNA damage resulting from an acute high UVR dose (80 µW cm -2 UV-B for 1.5 h) at a range of test temperatures (10, 15, 20, 25, and 30°C). 4. Larvae acclimated to 15°C and exposed to UVR at 15°C completely compensated UVR-induced DNA damage compared with 25°C acclimated larvae exposed to UVR at 25°C. Additionally, warm-acclimated larvae had higher CPDs than cold-acclimated larvae across test temperatures, which indicated a cost of living in warmer temperatures. In contrast, larvae reared under chronic elevated UVR levels showed no evidence of UVR acclimation resulting in lower DNA damage following an acute high UVR exposure. 5. Our finding that thermal acclimation in L. peronii larvae compensated UVR-induced DNA damage at low temperatures suggested that aquatic ectotherms living in cool temperatures may be more resilient to high UVR than previously realised. 6. We suggested in iduals or species with less capacity for thermal acclimation of DNA repair mechanisms may be more at risk if exposed to changing thermal and UVR exposure regimes but cautioned that thermal acclimation of DNA repair mechanisms may not always be beneficial.
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/MF13170
Abstract: Fish passage through road culverts is poorly understood, particularly for small-bodied fishes, despite this information being integral to the restoration of waterway connectivity. We assessed the prolonged swimming performance of a small-bodied fish, empire gudgeon (Hypseleotris compressa 3.2–7.7 cm total length, TL), and juvenile Australian bass (Percalates novemaculeata 3.5–7.8 cm TL). Swimming trials were conducted in a hydraulic flume across a range of fixed and increasing velocities in response to acute and long-term thermal treatments. A new statistical approach (Tobit analysis) was used to relate the thermal dependence of swimming endurance to hydraulic characteristics of culverts, providing estimates of maximum water velocity allowing upstream fish passage. Reductions in water temperature of 10°C, similar to those caused by cold-water releases from dams, significantly impaired critical swimming speeds of both species. Traversable water-velocity models identified H. compressa as a weak swimmer, requiring very low water velocities (≤0.10 m s–1 or 2.86 body lengths (BL) s–1) for unrestricted passage, whereas P. novemaculeata was predicted to traverse water velocities of ≤0.39 m s–1 or 12.12 BL s–1. Culvert designs can be improved by limiting water velocities to accommodate weak-swimming fishes and by accounting for the thermal sensitivity of swimming performance.
Publisher: Springer Science and Business Media LLC
Date: 08-12-2015
DOI: 10.1038/NCLIMATE2457
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/MF11229
Abstract: Patterns of movement in aquatic animals reflect ecologically important behaviours. Cyclical changes in the abiotic environment influence these movements, but when multiple processes occur simultaneously, identifying which is responsible for the observed movement can be complex. Here we used acoustic telemetry and signal processing to define the abiotic processes responsible for movement patterns in freshwater whiprays (Himantura dalyensis). Acoustic transmitters were implanted into the whiprays and their movements detected over 12 months by an array of passive acoustic receivers, deployed throughout 64 km of the Wenlock River, Qld, Australia. The time of an in idual’s arrival and departure from each receiver detection field was used to estimate whipray location continuously throughout the study. This created a linear-movement-waveform for each whipray and signal processing revealed periodic components within the waveform. Correlation of movement periodograms with those from abiotic processes categorically illustrated that the diel cycle dominated the pattern of whipray movement during the wet season, whereas tidal and lunar cycles dominated during the dry season. The study methodology represents a valuable tool for objectively defining the relationship between abiotic processes and the movement patterns of free-ranging aquatic animals and is particularly expedient when periods of no detection exist within the animal location data.
Publisher: American Physiological Society
Date: 08-2019
DOI: 10.1152/AJPREGU.00355.2018
Abstract: Chytridiomycosis, a lethal skin disease caused by the fungal pathogen Batrachochytrium dendrobatidis ( Bd), disrupts skin function of hibians, interfering with ionic and osmotic regulation. To regulate fungal loads, hibians increase their rate of skin sloughing. However, sloughing also causes a temporary loss of ionic and osmotic homeostasis due to disruption of the skin, a key osmoregulatory organ. The combined effects of increased sloughing frequency and chytridiomycosis contribute to the high rates of mortality from Bd infections. However, the mechanisms responsible for the loss of cutaneous osmotic regulation remain unknown. We measured the changes in whole animal water uptake rates, in vitro transcutaneous water fluxes across the ventral skin, and the mRNA expression of epithelial water transport proteins (aquaporins, AQPs) and junctional proteins in Bd-infected and uninfected Litoria caerulea skin. We hypothesize that infected frogs would show reduction/inhibition in cutaneous water transporters responsible for regulating water balance, and sloughing would exacerbate cutaneous water fluxes. We found that infected, nonsloughing frogs had an impaired rate of water uptake and showed increased rates of in vitro water efflux across the ventral skin. In uninfected frogs, the expression of AQPs and junction genes increased significantly with sloughing, which may assist in regulating cutaneous water movements and barrier function in the newly exposed skin. In contrast, infected frogs did not show this postsloughing increase in AQP gene expression. The combination of increased sloughing frequency, impaired water uptake rates, and increased rates of water loss likely contributes to the loss of osmotic homeostasis in frogs infected with Bd.
Publisher: Elsevier BV
Date: 05-1999
DOI: 10.1016/S0304-3940(99)00269-4
Abstract: The effect of N2 respiration on cerebral blood flow (CBF) velocity on the dorsal surface of cerebellum was examined in the estuarine crocodile, Crocodylus porosus, using epi-illumination microscopy. Twelve minutes of N2 respiration resulted in a 126% increase in CBF velocity. N2 respiration had no effect on blood pressure, indicating an underlying cerebral vasodilation. In addition, heart rate increased significantly. Systemic injections of aminophylline and the NO synthase (NOS) inhibitor nitro-L-arginine (L-NA) did not affect the hypoxia induced increase in CBF. We conclude that C. porosus responds to hypoxia with adenosine and nitric oxide (NO) independent cerebral vasodilation, and that this is likely to be a mechanism protecting the brain from energy deficiency during prolonged es.
Publisher: The Company of Biologists
Date: 07-2022
DOI: 10.1242/JEB.244376
Abstract: Many aquatically respiring animals acutely exposed to low pH waters suffer inhibition of ion uptake and loss of branchial (gill) epithelial integrity, culminating in a fatal loss of body Na+. Environmental calcium levels ([Ca2+]e) are pivotal in maintaining branchial junction integrity, with supplemental Ca2+ reversing the negative effects of low pH in some animals. Tolerance of some naturally acidic environments by aquatic animals is further complicated by low [Ca2+]e, yet many of these environments are surprisingly bio erse. How animals overcome the damaging actions of low pH and low environmental Ca2+ remains unknown. We examined the effects of [Ca2+]e on the response to low pH in larvae of the highly acid-tolerant frog Limnodynastes terraereginae. Acute exposure to low pH water in the presence of low (5 μmol l-1) [Ca2+]e increased net Na+ efflux. Provision of additional [Ca2+]e reduced net Na+ efflux, but the effect was saturable. Acclimation to both low and high (250 μmol l-1) [Ca2+]e improved the resistance of larvae to Na+ efflux at low pH. Exposure to the Ca2+ channel inhibitor ruthenium red resulted in an abrupt loss of tolerance in low pH-acclimated larvae. Acclimation to acidic water increased branchial gene expression of the intracellular Ca2+ transport protein calbindin, consistent with a role for increased transcellular Ca2+ trafficking in the tolerance of acidic water. This study supports a role for [Ca2+]e in promoting branchial integrity and highlights a potential mechanism via the maintenance of transcellular Ca2+ uptake in the acid tolerance of L. terraereginae larvae.
Publisher: The Company of Biologists
Date: 15-05-2009
DOI: 10.1242/JEB.028951
Abstract: A virulent strain of the obligate intracellular bacterium Wolbachia pipientis that shortens insect lifespan has recently been transinfected into the primary mosquito vector of dengue virus, Aedes aegypti L. The microbe's ability to shorten lifespan and spread through host populations under the action of cytoplasmic incompatibility means it has the potential to be used as a biocontrol agent to reduce dengue virus transmission. Wolbachia is present in many host tissues and may have local effects on erse biological processes. In other insects, Wolbachiainfections have been shown to alter locomotor activity and response time to food cues. In mosquitoes, locomotor performance relates to the location of mates, human hosts, resting sites and oviposition sites. We have therefore examined the effect of the virulent, life-shortening Wolbachia strain wMelPop on the locomotion of Ae. aegypti as they age and as the pathogenicity of the infection increases. In parallel experiments we also examined CO2 production as a proxy for metabolic rate, to investigate a potential mechanistic explanation for any changes in locomotion. Contrary to expectation, we found that the infection increased activity and metabolic rate and that these effects were relatively consistent over the insect's lifespan. The results do not fit a standard model of bacterial pathogenesis in insects, and instead may reveal additional physiological changes induced by infection, such as either increased hunger or defects in the nervous system.
Publisher: The Royal Society
Date: 07-07-2010
Abstract: Population decline and a shift in the geographical distribution of some ectothermic animals have been attributed to climatic warming. Here, we show that rises in water temperature of a few degrees, while within the thermal window for locomotor performance, may be detrimental to ing behaviour in air-breathing ectotherms (turtles, crocodilians, marine iguanas, hibians, snakes and lizards). Submergence times and internal and external body temperature were remotely recorded from freshwater crocodiles ( Crocodylus johnstoni ) while they free-ranged throughout their natural habitat in summer and winter. During summer, the crocodiles' mean body temperature was 5.2 ± 0.1°C higher than in winter and the largest proportion of total e time was composed of e durations approximately 15 min less than in winter. Diving beyond 40 min during summer required the crocodiles to exponentially increase the time they spent on the surface after the e, presumably to clear anaerobic debt. The relationship was not as significant in winter, even though a greater proportion of es were of a longer duration, suggesting that ing lactate threshold (DLT) was reduced in summer compared with winter. Additional evidence for a reduced DLT in summer was derived from the stronger influence body mass exerted upon e duration, compared to winter. The results demonstrate that the higher summer body temperature increased oxygen demand during the e, implying that thermal acclimatization of the ing metabolic rate was inadequate. If the study findings are common among air-breathing ing ectotherms, then long-term warming of the aquatic environment may be detrimental to behavioural function and survivorship.
Publisher: Elsevier BV
Date: 10-2021
DOI: 10.1016/0167-0115(95)00055-G
Abstract: The two aortas of the crocodile are in open connection at two sites, the foramen of Panizzae immediately outside the ventricles, and the arterial anastomosis at the level of the gut. The present study was performed to elucidate the innervation of the cardiovascular structures of the crocodile, in part to provide a further basis for the assumption that the apertures of the foramen and the anastomosis may be altered, possibly leading to changes in the flow profiles of the central vessels. The presence of smooth muscle arranged at the circumference of the foramen and in the walls of the anastomosis was demonstrated. The cardiovascular structures were innervated by nerves containing co-existing tyrosine hydroxylase, NPY and somatostatin immunoreactivities, which also occurred in neurons of the sympathetic ganglia. CGRP and substance P immunoreactive material co-existed in cardiovascular nerves, and in the nodose ganglion. In addition, bombesin, VIP and galanin immunoreactive nerves were found. Effects of neuropeptides on blood flows and blood pressures were studied in vivo. Substance P increased all blood flows measured, NPY increased the flow through the arterial anastomosis while neurotensin caused an initial decrease in the flow through the arterial anastomosis. In conclusion, there is a rich innervation of the heart and major vessels of the estuarine crocodile, including the foramen of Panizza and the arterial anastomosis. These nerves possibly regulate the distribution of blood in the cardiovascular system, which is further suggested by the results of the injection of neuropeptides.
Publisher: Wiley
Date: 05-1995
Publisher: The Company of Biologists
Date: 15-06-2023
DOI: 10.1242/JEB.246317
Publisher: The Company of Biologists
Date: 15-11-2009
DOI: 10.1242/JEB.027748
Abstract: Although green striped burrowing frogs (Cyclorana alboguttata)experience large reductions in the mass and absorptive surface area of the small intestine (SI) during aestivation, little is known about how this may affect the functional capacity of the SI. We examined changes in the function(l-proline uptake rate and capacity) and metabolism of the SI(in vitro oxygen consumption, Na+/K+-ATPase activity and abundance) of C. alboguttata following 6 months of aestivation. l-Proline uptake rate was significantly higher in aestivating frogs, but overall uptake capacity was lower than in active frogs. Total SI oxygen consumption rate (VO2) was also lower in aestivating frogs, despite no difference in mass-specific V̇O2. The proportion of intestinal V̇O2 associated with Na+/K+-ATPase activity and protein synthesis was equivalent between active and aestivating frogs, suggesting these processes were unaffected by aestivation. Indeed, the activity of Na+/K+-ATPase transporters in the SI of aestivating frogs was not different from that of active animals. Aestivating frogs maintained Na+/K+-ATPase activity, despite experiencing a reduction in the density of Na+/K+-ATPase transporters, by increasing the molecular activity of the remaining pumps to 2–3 times that of active frogs. These results show that functionality of the SI is maintained at the cellular level, potentially facilitating the reclamation of nutrients from the intestinal lumen while in aestivation. Despite this, the functional capacity of the SI in aestivating C. alboguttata is significantly reduced due to a reduction in tissue mass,helping frogs to conserve energy while in aestivation.
Publisher: Wiley
Date: 05-1989
Publisher: Wiley
Date: 03-2003
Publisher: Springer Science and Business Media LLC
Date: 22-06-2006
DOI: 10.1007/S00360-006-0095-6
Abstract: In aquatic vertebrates that acquire oxygen aerially e duration scales positively with body mass, i.e. larger animals can e for longer periods, however in bimodally respiring animals the relationship between e duration and body mass is unclear. In this study we investigated the relationships between body size, aquatic respiration, and e duration in the bimodally respiring turtle, Elseya albagula. Under normoxic conditions, e duration was found to be independent of body mass. The e durations of smaller turtles were equivalent to that of larger in iduals despite their relatively smaller oxygen stores and higher mass specific metabolic rates. Smaller turtles were able to increase their e duration through the use of aquatic respiration. Smaller turtles had a relatively higher cloacal bursae surface area than larger turtles, which allowed them to extract a relatively larger amount of oxygen from the water. By removing the ability to respire aquatically (hypoxic conditions), the e duration of the smaller turtles significantly decreased restoring the normal positive relationship between body size and e duration that is seen in other air-breathing vertebrates.
Publisher: Springer Science and Business Media LLC
Date: 07-05-2001
Abstract: We examined the burst swimming performance of two Antarctic fishes, Trematomus bernacchii and T. centronotus, at five temperatures between -1 degrees C and 10 degrees C. As Antarctic fishes are considered one of the most cold specialised and stenothermal of all ectotherms, we predicted they would possess a narrow thermal performance breadth for burst swimming and a correlative decrease in performance at high temperatures. Burst swimming was assessed by videotaping swimming sequences with a 50-Hz video camera and analysing the sequences frame-by-frame to determine maximum velocity, the distance moved throughout the initial 200 ms, and the time taken to reach maximum velocity. In contrast to our prediction, we found both species possessed a wide thermal performance breadth for burst swimming. Although maximum swimming velocity for both T. bernacchii and T. centronotus was significantly highest at 6 degrees C, maximum velocity at all other test temperatures was less than 20% lower. Thus, it appears that specialisation to a highly stable and cold environment is not necessarily associated with a narrow thermal performance breadth for burst swimming in Antarctic fish. We also examined the ability of the Antarctic fish Pagothenia borchgrevinki to acclimate their burst-swimming performance to different temperatures. We exposed P. borchgrevinki to either -1 degrees C or 4 degrees C for 4 weeks and tested their burst-swimming performance at four temperatures between -1 degrees C and 10 degrees C. Burst-swimming performance of Pagothenia borchgrevinki was unaffected by exposure to either -1 degrees C or 4 degrees C for 4 weeks. Maximum swimming velocity of both acclimation groups was thermally independent over the total temperature range of 1 degrees C to 10 degrees C. Therefore, the loss of any capacity to restructure the phenotype and an inability to thermally acclimate swimming performance appears to be associated with inhabiting a highly stable thermal environment.
Publisher: The Royal Society
Date: 08-2016
Abstract: Temperature and ultraviolet B (UV-B) interact in causing cellular damage and impairing locomotor performance. Here, we test the hypothesis that movement and thermal selection of zebrafish ( Danio rerio ) change in the presence of UV-B, and in particular, that fish which were chronically exposed to UV-B avoid high and low temperature extremes to maximize activities of antioxidant enzymes. Fish chronically (two to three weeks) exposed to UV-B had increased reactive oxygen species (ROS)-induced damage to proteins and membranes, and reduced swimming performance at high (more than 26°C) temperatures. In an open field arena with a thermal gradient, chronically exposed fish avoided high and low temperature extremes compared with control fish. Additionally, both control and chronically exposed fish showed slower voluntary swimming speeds in the presence of UV-B. We suggest that in the presence of UV-B fish may reduce muscular activity to minimize intrinsic ROS production. Our data show that the interaction between UV-B and temperature determines movement and microhabitat selection of fish, which is therefore of ecological importance particularly in anthropogenically modified environments.
Publisher: Elsevier BV
Date: 08-2007
Publisher: The Company of Biologists
Date: 05-2008
DOI: 10.1242/JEB.015636
Abstract: The estuarine crocodile, Crocodylus porosus, inhabits both freshwater and hypersaline waterways and maintains ionic homeostasis by excreting excess sodium and chloride ions via lingual salt glands. In the present study, we sought to investigate the phenotypic plasticity, both morphological and functional, in the lingual salt glands of the estuarine crocodile associated with chronic exposure to freshwater (FW) and saltwater(SW) environments. Examination of haematological parameters indicated that there were no long-term disruptions to ionic homeostasis with prolonged exposure to SW. Maximal secretory rates from the salt glands of SW-acclimated animals (100.8±14.7 μmol 100 g–0.7 body mass h–1) were almost three times greater than those of FW-acclimated animals (31.6±6.2 μmol 100 g–0.7 body mass h–1). There were no differences in the mass-specific metabolic rate of salt gland tissue slices from FW- and SW-acclimated animals(558.9±49.6 and 527.3±142.8 μl O2g–1 h–1, respectively). Stimulation of the tissue slices from SW-acclimated animals by methacholine resulted in a 33%increase in oxygen consumption rate. There was no significant increase in the metabolic rate of tissues from FW-acclimated animals in response to methacholine. Morphologically, the secretory cells from the salt glands of SW-acclimated animals were larger than those of FW-acclimated animals. In addition, there were significantly more mitochondria per unit volume in secretory tissue from SW-acclimated animals. The results from this study demonstrate that the salt glands of C. porosus are phenotypically plastic, both morphologically and functionally and acclimate to changes in environmental salinity.
Publisher: Elsevier BV
Date: 09-2002
Publisher: The Company of Biologists
Date: 2023
DOI: 10.1242/JEB.245455
Publisher: Elsevier BV
Date: 04-1996
Abstract: Vasoactive intestinal peptide (VIP)-like immunoreactivity was demonstrated in the lingual salt glands of the estuarine crocodile, Crocodylus porosus. Varicose fibers showing VIP-like immunoreactivity ramified the salt glands, forming a dense network around the basal region of the exocrine cells. Secretions from the lingual salt glands were monitored in hatchling C. porosus. Spontaneous secretory activity was variable, ranging from 0.3 to 5.3 micromol Na 100 g(-0.7) bm hr(-1) (bm, body mass). Administration of a 100-microl bolus of 0.9% NaCl, via a cannulated femoral vein, did not affect the spontaneous secretory rate. However, injection of 100 pmol porcine VIP resulted in a massive increase in secretory activity, reaching a maximum of 58.2 micromol of Na 100 g(-0.7) bm hr(-1). The presence of VIP-like immunoreactivity and the positive secretory effect of administered VIP indicate a potential action of VIP on salt gland activity.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/MF14042
Abstract: Underwater passive acoustic (PA) telemetry is becoming the preferred technology for investigating animal movement in aquatic systems however, much of the current statistical tools for telemetry data were established from global positioning system (GPS)-based data. To understand the appropriateness of these tools for PA telemetry, we dual-tagged free-ranging aquatic animals that exist at the air-water interface (Crocodylus porosus, n=14). The location of each animal was simultaneously recorded over a 3-month period by fixed acoustic receivers and satellite positioning. Estimates of minimum travel distance and home range (HR) were then calculated from the PA and GPS datasets. The study revealed significant disparity between telemetry technologies in estimates of minimum travel distance and HR size. Of the five HR measures investigated, the linear distance measure produced the most comparable estimates of HR size and overlap. The kernel utilisation distribution with a reference smoothing parameter function and ad hoc function, however, produced comparable estimates when raw acoustic detections were grouped into periods when animals were within and between receiver detection fields. The study offers guidelines on how to improve the accuracy and precision of space-use estimates from PA telemetry, even in receiver arrangements with large areas of non-detection.
Publisher: Elsevier BV
Date: 09-1997
Publisher: Elsevier BV
Date: 02-1992
Publisher: Wiley
Date: 19-04-2006
DOI: 10.1111/J.1365-2656.2006.01089.X
Abstract: 1. To survive adverse or unpredictable conditions in the ontogenetic environment, many organisms retain a level of phenotypic plasticity that allows them to meet the challenges of rapidly changing conditions. Larval anurans are widely known for their ability to modify behaviour, morphology and physiological processes during development, making them an ideal model system for studies of environmental effects on phenotypic traits. Although temperature is one of the most important factors influencing the growth, development and metamorphic condition of larval anurans, many studies have failed to include ecologically relevant thermal fluctuations among their treatments. 2. We compared the growth and age at metamorphosis of striped marsh frogs Limnodynastes peronii raised in a diurnally fluctuating thermal regime and a stable regime of the same mean temperature. We then assessed the long-term effects of the larval environment on the morphology and performance of post-metamorphic frogs. 3. Larval L. peronii from the fluctuating treatment were significantly longer throughout development and metamorphosed about 5 days earlier. Frogs from the fluctuating group metamorphosed at a smaller mass and in poorer condition compared with the stable group, and had proportionally shorter legs. 4. Frogs from the fluctuating group showed greater jumping performance at metamorphosis and less degradation in performance during a 10-week dormancy. Treatment differences in performance could not be explained by whole-animal morphological variation, suggesting improved contractile properties of the muscles in the fluctuating group.
Publisher: Cold Spring Harbor Laboratory
Date: 02-09-2022
DOI: 10.1101/2022.09.01.506274
Abstract: Anthropogenic ozone depletion has led to a 2-5% increase in ultraviolet B radiation (UVBR) levels reaching the earth’s surface. Exposure to UVBR causes harmful DNA damage in hibians, but this is minimized by DNA repair enzymes such as thermally sensitive CPD-photolyase, with cool temperatures slowing repair rates. It is unknown whether hibian species differ in the repair response to a given dose of UVBR across temperatures. We reared larvae of three species ( Limnodynastes peronii , Limnodynastes tasmaniensis , and Platyplectrum ornatum) at 25°C and acutely exposed them to 80 μW cm −2 UVBR for 2 h at either 20°C or 30°C. UVBR-mediated DNA damage was measured as larvae repaired damage in photoreactive light at their exposure temperatures. Cool temperatures increased DNA damage in all two species and slowed DNA repair rate in P. ornatum . The magnitude of DNA damage incurred from UVBR was species-specific. P. ornatum had the lowest CPDs and DNA repair rates, and the depressive effects of low temperature on photorepair were greater in L. tasmaniensis . Considering the susceptibility of most aquatic organisms to UVBR, this research highlighted a need to consider the complexity of species-specific physiology when forecasting the influence of changing UVBR and temperature in aquatic ecosystems.
Publisher: The Company of Biologists
Date: 15-02-2021
DOI: 10.1242/JEB.228213
Abstract: Diving ectothermic vertebrates are an important component of many aquatic ecosystems, but the threat of climate warming is particularly salient to this group. Dive durations typically decrease as water temperatures rise yet, we lack an understanding of whether this trend is apparent in all ing ectotherms and how this group will fare under climate warming. We compiled data from 27 studies on 20 ectothermic vertebrate species to quantify the effect of temperature on e durations. Using meta-analytic approaches, we show that, on average, e durations decreased by 11% with every 1°C increase in water temperature. Larger increases in temperature (e.g. +3°C versus +8–9°C) exerted stronger effects on e durations. Although species that respire bimodally are projected to be more resilient to the effects of temperature on e durations than purely aerial breathers, we found no significant difference between these groups. Body mass had a weak impact on mean e durations, with smaller ers being impacted by temperature more strongly. Few studies have examined thermal phenotypic plasticity (N=4) in ing ectotherms, and all report limited plasticity. Average water temperatures in marine and freshwater habitats are projected to increase between 1.5 and 4°C in the next century, and our data suggest that this magnitude of warming could translate to substantial decreases in e durations, by approximately 16–44%. Together, these data shed light on an overlooked threat to ing ectothermic vertebrates and suggest that time available for underwater activities, such as predator avoidance and foraging, may be shortened under future warming.
Publisher: American Physiological Society
Date: 15-05-2013
DOI: 10.1152/PHYSIOLGENOMICS.00163.2012
Abstract: Green-striped burrowing frogs ( Cyclorana alboguttata ) survive in arid environments by burrowing underground and entering into a deep, prolonged metabolic depression known as estivation. Throughout estivation, C. alboguttata is immobilized within a cast-like cocoon of shed skin and ceases feeding and moving. Remarkably, these frogs exhibit very little muscle atrophy despite extended disuse and fasting. Little is known about the transcriptional regulation of estivation or associated mechanisms that may minimize degradative pathways of atrophy. To investigate transcriptional pathways associated with metabolic depression and maintenance of muscle function in estivating burrowing frogs, we assembled a skeletal muscle transcriptome using next-generation short read sequencing and compared gene expression patterns between active and 4 mo estivating C. alboguttata . This identified a complex suite of gene expression changes that occur in muscle during estivation and provides evidence that estivation in burrowing frogs involves transcriptional regulation of genes associated with cytoskeletal remodeling, avoidance of oxidative stress, energy metabolism, the cell stress response, and apoptotic signaling. In particular, the expression levels of genes encoding cell cycle and prosurvival proteins, such as serine/threonine-protein kinase Chk1, cell ision protein kinase 2, survivin, and vesicular overexpressed in cancer prosurvival protein 1, were upregulated during estivation. These data suggest that estivating C. alboguttata are able to regulate the expression of genes in several major cellular pathways critical to the survival and viability of cells, thus preserving muscle function while avoiding the deleterious consequences often seen in laboratory models of muscle disuse.
Publisher: Wiley
Date: 29-11-2018
DOI: 10.1111/JFB.13514
Abstract: This study compared the critical swimming speed (U
Publisher: Springer Science and Business Media LLC
Date: 10-1994
DOI: 10.1007/BF00239050
Publisher: Springer Science and Business Media LLC
Date: 08-01-2012
DOI: 10.1007/S00360-011-0643-6
Abstract: The presumption that organisms benefit from thermal acclimation has been widely debated in the literature. The ability to thermally acclimate to offset temperature effects on physiological function is prevalent in ectotherms that are unable to thermoregulate year-round to maintain performance. In this study we examined the physiological and behavioural consequences of long-term exposure to different water temperatures in the aquatic snake Acrochordus arafurae. We hypothesised that long es would benefit this species by reducing the likelihood of avian predation. To achieve longer es at high temperatures, we predicted that thermal acclimation of A. arafurae would reduce metabolic rate and increase use of aquatic respiration. Acrochordus arafurae were held at 24 or 32°C for 3 months before e duration and physiological factors were assessed (at both 24 and 32°C). Although filesnakes demonstrated thermal acclimation of metabolic rate, use of aquatic respiration was thermally independent and did not acclimate. Mean e duration did not differ between the acclimation groups at either temperature however, warm-acclimated animals increased maximum and modal e duration, demonstrating a longer e duration capacity. Our study established that A. arafurae is capable of thermal acclimation and this confers a benefit to the ing abilities of this snake.
Publisher: Elsevier BV
Date: 10-2019
Publisher: Wiley
Date: 02-09-2012
Publisher: Elsevier BV
Date: 02-2019
Publisher: Cold Spring Harbor Laboratory
Date: 16-12-2019
DOI: 10.1101/2019.12.15.872259
Abstract: In the coastal sandy lowlands of east Australia, several anuran species including the Cooloola Sedgefrog Litoria cooloolensis , show remarkable tolerance to dilute highly acidic waters as low as pH 3.5. To investigate the physiological and morphological underpinnings of acid tolerance in L. cooloolensis larvae, we compared Na + balance, uptake and efflux rates, and gill and skin morphology in larvae reared in circum-neutral (pH 6.5) and pH 3.5 water. We hypothesised that acute exposure to pH 3.5 water would cause an initial loss of ionic homeostasis in larvae, but with chronic exposure larvae would restore Na + balance. Net Na + flux rates were not significantly different from zero in larvae reared at pH 3.5 and in acid-na& iumlve animals maintained in pH 6.5 water. Animals reared at pH 6.5 and acutely exposed to pH 3.5 exhibited a net loss of Na + , due to a significant inhibition of Na + uptake. In contrast, L. cooloolensis larvae reared at pH 3.5 maintained Na + balance at pH 3.5 and did not exhibit inhibition of Na + uptake at this pH. Investigation of Na + transport kinetics and the morphology of the gills and integument suggests tolerance of L. cooloolensis larvae to low pH may be attributed to a high capacity for branchial Na + uptake, increased tight junction length and elevated mucus production in the gills and integument. These factors confer resistance to acid damage and disruption of ionic homeostasis which would otherwise result in the death of larvae exposed to waters of pH 4.0 and less.
Publisher: Wiley
Date: 07-1992
Publisher: Wiley
Date: 26-07-2013
DOI: 10.1111/FWB.12206
Publisher: The Company of Biologists
Date: 15-11-2011
DOI: 10.1242/JEB.054148
Abstract: Reactive oxygen species (ROS), produced commensurate with aerobic metabolic rate, contribute to muscle disuse atrophy (MDA) in immobilised animals by damaging myoskeletal protein and lipids. Aestivating frogs appear to avoid MDA in part by substantially suppressing metabolic rate. However, as ectotherms, metabolic rate is sensitive to environmental temperature, and the high ambient temperatures that may be experienced by frogs during aestivation could in fact promote MDA. In this study, we investigated the effect of temperature on the metabolic rate of the aestivating frog Cyclorana alboguttata and its skeletal muscles in order to determine their likely susceptibility to MDA. Compared with non-aestivating frogs, a significant decrease in metabolic rate was recorded for aestivating frogs at 20, 24 and 30°C. At 30°C, however, the metabolic rate of aestivating frogs was significantly higher, approximately double that of frogs aestivating at 20 or 24°C, and the magnitude of the metabolic depression was significantly reduced at 30°C compared with that at 20°C. Temperature effects were also observed at the tissue level. At 24 and 30°C the metabolic rate of all muscles from aestivating frogs was significantly depressed compared with that of muscles from non-aestivating frogs. However, during aestivation at 30°C the metabolic rates of gastrocnemius, sartorius and cruralis were significantly elevated compared with those from frogs aestivating at 24°C. Our data show that the metabolism of C. alboguttata and its skeletal muscles is elevated at higher temperatures during aestivation and that the capacity of the whole animal to actively depress metabolism is impaired at 30°C.
Publisher: Springer Science and Business Media LLC
Date: 27-07-2005
DOI: 10.1007/S00360-005-0007-1
Abstract: The thermal dependence of biochemical reaction rates means that many animals regulate their body temperature so that fluctuations in body temperature are small compared to environmental temperature fluctuations. Thermoregulation is a complex process that involves sensing of the environment, and subsequent processing of the environmental information. We suggest that the physiological mechanisms that facilitate thermoregulation transcend phylogenetic boundaries. Reptiles are primarily used as model organisms for ecological and evolutionary research and, unlike in mammals, the physiological basis of many aspects in thermoregulation remains obscure. Here, we review recent research on regulation of body temperature, thermoreception, body temperature set-points, and cardiovascular control of heating and cooling in reptiles. The aim of this review is to place physiological thermoregulation of reptiles in a wider phylogenetic context. Future research on reptilian thermoregulation should focus on the pathways that connect peripheral sensing to central processing which will ultimately lead to the thermoregulatory response.
Publisher: Cold Spring Harbor Laboratory
Date: 21-09-2023
Publisher: Springer Science and Business Media LLC
Date: 12-12-2014
DOI: 10.1007/S00360-014-0880-6
Abstract: In most mammals, prolonged muscle disuse (e.g. bed-rest, limb casting or spaceflight) results in atrophy of muscle fibres which is largely due to unregulated proteolysis. Although numerous proteolytic pathways are known to participate in muscle disuse atrophy, recent evidence suggests that activation of Ca²⁺-dependent cysteine proteases (calpains) is required for disuse atrophy in limb skeletal muscles. In contrast to typical models of muscle disuse (humans and rodents), animals that experience natural bouts of chronic muscle inactivity, such as hibernating mammals and aestivating frogs, consistently exhibit limited or no change in skeletal muscle size. In the current study, we examined enzyme activity, protein abundance and gene expression levels of calpain isoforms in gastrocnemius muscle of the aestivating frog, Cyclorana alboguttata. We predicted that in aestivating C. alboguttata there would be a downregulation of the abundance, activity and gene expression of calpain 1 and calpain 2. In contrast to our hypothesis, there was no significant decrease in the enzyme activity levels or the relative protein abundances of calpain 1 and calpain 2. Similarly, gene expression assays (both qRT-PCR and RNA Seq data) indicated that calpains were unaffected by aestivation. Western blotting of 'muscle-specific' calpain 3, which is consistently downregulated during atrophic conditions, indicated that this isoform is present in C. alboguttata muscle where it appears to be in its autolysed state. The absence of any increase in enzyme activity, protein and mRNA abundance of calpains in aestivators is consistent with the protection of gastrocnemius muscle against uncontrolled proteolysis throughout aestivation.
Publisher: Wiley
Date: 28-07-2008
Publisher: Inter-Research Science Center
Date: 21-06-2017
DOI: 10.3354/MEPS12200
Publisher: The Company of Biologists
Date: 06-2017
DOI: 10.1242/JEB.151738
Abstract: Amphibian skin is a multifunctional organ providing protection from the external environment and facilitating the physiological exchange of gases, water and salts with the environment. In order to maintain these functions, the outer layer of skin is regularly replaced in a process called sloughing. During sloughing, the outermost layer of the skin is removed in its entirety, which has the potential to interfere with skin permeability and ion transport, disrupting homeostasis. In this study, we measured, in vivo, the effects of sloughing on the cutaneous efflux of ions in toads Rhinella marina kept in freshwater conditions. We also measured transepithelial potential, cutaneous resistance, active ion transport and the distribution, abundance and gene expression of the key ion transport proteins sodium–potassium ATPase (NKA) and epithelial sodium channel (ENaC) during sloughing. We hypothesised that the increase in transepithelial efflux of ions during sloughing is a consequence of increased permeability and/or a reduction in the abundance or expression of cutaneous ion transport proteins, resulting in disruption of internal ion homeostasis. There was a significant increase in sodium and chloride efflux during sloughing in R. marina. However, although in vitro skin resistance decreased after sloughing, active sodium transport increased commensurate with an increase in NKA and ENaC protein abundance in the skin. These changes in skin function associated with sloughing did not affect the maintenance of internal electrolyte homeostasis. These results suggest that during sloughing, hibians actively maintain internal homeostasis by increasing cutaneous rates of ion uptake.
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/ZO05001
Abstract: Many marine reptiles and birds possess extrarenal salt glands that facilitate the excretion of excess sodium and chloride ions accumulated as a consequence of living in saline environments. Control of the secretory activity of avian salt glands is under neural control, but little information is available on the control of reptilian salt glands. Innervation of the lingual salt glands of the salt water crocodile, Crocodylus porosus, was examined in salt water-acclimated animals using histological methods. Extensive networks of both cholinergic and adrenergic nerve fibres were identified close to salt-secreting lobules and vasculature. The identification of both catecholamine-containing and cholinergic neurons in the salt gland epithelium and close to major blood vessels in the tissue suggests the action of the neurotransmitters on the salt-secreting epithelium itself and the rich vascular network of the lingual salt glands.
Publisher: Wiley
Date: 02-2022
DOI: 10.1111/GCB.16088
Abstract: Climate and land‐use changes are expected to increase the future occurrence of wildfires, with potentially devastating consequences for freshwater species and ecosystems. Wildfires that burn in close proximity to freshwater systems can significantly alter the physicochemical properties of water. Following wildfires and heavy rain, freshwater species must contend with complex combinations of wildfire ash components (nutrients, polycyclic aromatic hydrocarbons, and metals), altered light and thermal regimes, and periods of low oxygen that together can lead to mass mortality events. However, the responses of aquatic fauna to wildfire disturbances are poorly understood. Here we provide a systematic review of available evidence on how aquatic animals respond to and recover from wildfire disturbance. Two databases (Web of Science and Scopus) were used to identify key literature. A total of 83 studies from across 11 countries were identified to have assessed the risk of wildfires on aquatic animals. We provide a summary of the main ecosystem‐level changes associated with wildfires and the main responses of aquatic fauna to such disturbances. We pay special focus to physiological tools and biomarkers used to assess how wildfires impact aquatic animals. We conclude by providing an overview of how physiological biomarkers can further our understanding of wildfire‐related impacts on aquatic fauna, and how different physiological tools can be incorporated into management and conservation plans and serve as early warning signs of wildfire disturbances.
Publisher: Wiley
Date: 05-1995
Publisher: Elsevier BV
Date: 1993
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/MF07250
Abstract: Temperature profoundly influences virtually all aspects of fish biology. Barramundi, Lates calcarifer Bloch, 1790, is a catadromous fish that undergoes several migrations in its life cycle, necessitating locomotion under various thermal conditions. The present study examined the effects of varying thermal regimes on performance in juvenile L. calcarifer by determining the effects of rearing and ambient temperature on burst (Umax) and sustained (Ucrit) swimming ability. Fish were incubated at three set temperatures, 26°C (cool), 29°C (control) and 31°C (warm), from egg fertilisation until first feeding before some of the larvae were allocated to different temperatures to differentiate the effects of incubation temperature v. rearing temperature on subsequent swimming performance. In iduals incubated and reared at the cool (26°C) temperature showed significantly faster burst speeds at the 26°C test temperature than fish from any other treatment group. This indicates the ability of L. calcarifer to thermally acclimate burst swimming. However, there was no evidence that incubation temperature (as opposed to rearing temperature) affected burst or sustained swimming ability. Swimming ability was significantly affected by the test temperature, with the Umax of fish highest at the 29°C test temperature. Lower test temperatures depressed both burst and sustained swimming ability. Juvenile L. calcarifer can acclimate Umax, but swimming ability was unaffected by incubation thermal history.
Publisher: Springer Science and Business Media LLC
Date: 03-2023
DOI: 10.1007/S00265-023-03303-Z
Abstract: In species where conflict is costly, in iduals adopt alternative movement tactics to minimise the risk of competitive interactions. Dominant males often maintain defined territories, while less competitive males may be forced to adopt alternative tactics to maximise fitness and reduce conflict. However, the extent to which males switch tactics according to current social or physiological status is poorly understood. Using implanted acoustic tags and a fixed array of tracking receivers, we investigated how the behaviour of 78 male estuarine crocodiles ( Crocodylus porosus ) shifted over an 11-year period in relation to ontogeny, body condition, and the extent of physical injuries. We discovered that male crocodiles sorted into three common movement classes, with 51% of males maintaining the same movement class across consecutive years (max = 9 years). Males 4 m in total length maintained confined territories both within and across years and had the greatest extent of injuries and the highest condition score, indicative of territory holders. In contrast, smaller males sorted into high movement roamer or low movement site-philopatric tactics, where the tactic an in idual adopted was less stable between years and did not correlate with condition or external injuries. Our study reveals the socio-biological mechanisms by which estuarine crocodiles coexist within a restricted habitat. Identifying in idual-level differences in movement helps us predict which in iduals are more likely to be involved in human-wildlife interactions. However, studying long-term shifts in movement is challenging, as large datasets of co-occurring in iduals tracked in their natural environment over multiple years are required. We tracked a population of 78 male estuarine crocodiles (1030–4687 mm total length) in a shared environment over 11 years and assessed how eight movement traits were linked to body size and physical condition. At the population level, males sorted into different movement tactics according to ontogeny, with large territorial males having better body condition yet a greater incidence of injury. However, 49% of males showed variability across years, suggesting that tactics were conditional relative to environmental variability and a male’s own status. Our study provides insights into the mechanisms and costs of movement tactics in wild crocodile populations.
Publisher: Springer Science and Business Media LLC
Date: 27-02-2018
DOI: 10.1038/S41598-018-22002-8
Abstract: Sloughing maintains the skins integrity and critical functionality in hibians. Given the behavioural, morphological and osmoregulatory changes that accompany sloughing, this process is likely to be physiologically costly. Chytridiomycosis, a cutaneous disease of hibians caused by the fungus Batrachochytrium dendrobatidis ( Bd ), disrupts skin function and increases sloughing rates. Moreover, mortality rates from chytridiomycosis are significantly higher in juveniles and so we hypothesised that smaller in iduals maybe more susceptible to chytridiomycosis because of allometric scaling effects on the energetic and osmoregulatory costs of sloughing. We measured in-vivo cutaneous ion loss rates and whole animal metabolic rate (MR) of Green tree frogs, Litoria caerulea , over a range of body sizes both infected and uninfected frogs during sloughing. Infected animals had a greater rate of ion loss and mass-specific MR during non-sloughing periods but there were no additional effects of sloughing on either of these parameters. There were also significant interactions with body size and Bd load indicating that smaller animals with higher Bd loads have greater rates of ion loss and higher energetic demands. Our results shed light on why smaller Bd -infected anurans often exhibit greater physiological disruption than larger in iduals.
Publisher: Wiley
Date: 15-04-2008
Publisher: The Royal Society
Date: 17-11-2010
Abstract: Mucus performs numerous protective functions in vertebrates, and in fishes may defend them against harmful organisms, although often the evidence is contradictory. The function of the mucous cocoons that many parrotfishes and wrasses sleep in, while long used as a classical ex le of antipredator behaviour, remains unresolved. Ectoparasitic gnathiid isopods (Gnathiidae), which feed on the blood of fish, are removed by cleaner fish during the day however, it is unclear how parrotfish and wrasse avoid gnathiid attacks at night. To test the novel hypothesis that mucous cocoons protect against gnathiids, we exposed the coral reef parrotfish Chlorurus sordidus (Scaridae) with and without cocoons to gnathiids overnight and measured the energetic content of cocoons. Fish without mucous cocoons were attacked more by gnathiids than fish with cocoons. The energetic content of mucous cocoons was estimated as 2.5 per cent of the fish's daily energy budget fish. Therefore, mucous cocoons protected against attacks by gnathiids, acting like mosquito nets in humans, a function of cocoons and an efficient physiological adaptation for preventing parasite infestation that is not used by any other animal.
Publisher: Elsevier BV
Date: 03-1992
Publisher: Elsevier BV
Date: 11-1993
DOI: 10.1016/0034-5687(93)90046-D
Abstract: Simultaneous measurements of pulmonary blood flow (qPA), coeliacomesenteric blood flow (qCoA), dorsal aortic blood pressure (PDA), heart rate (fH) and branchial ventilation frequency (fv) were made in the Australian lungfish, Neoceratodus forsteri, during air breathing and aquatic hypoxia. The cholinergic and adrenergic influences on the cardiovascular system were investigated during normoxia using pharmacological agents, and the presence of catecholamines and serotonin in different tissues was investigated using histochemistry. Air breathing rarely occurred during normoxia but when it did, it was always associated with increased pulmonary blood flow. The pulmonary vasculature is influenced by both a cholinergic and adrenergic tonus whereas the coeliacomesenteric vasculature is influenced by a beta-adrenergic vasodilator mechanism. No adrenergic nerve fibers could be demonstrated in Neoceratodus but catecholamine-containing endothelial cells were found in the atrium of the heart. In addition, serotonin-immunoreactive cells were demonstrated in the pulmonary epithelium. The most prominent response to aquatic hypoxia was an increase in gill breathing frequency followed by an increased number of air breaths together with increased pulmonary blood flow. It is clear from the present investigation that Neoceratodus is able to match cardiovascular performance to meet the changes in respiration during hypoxia.
Publisher: The Company of Biologists
Date: 04-2003
DOI: 10.1242/JEB.00222
Abstract: The effect of heating and cooling on heart rate in the estuarine crocodile Crocodylus porosus was studied in response to different heat transfer mechanisms and heat loads. Three heating treatments were investigated. C. porosus were: (1) exposed to a radiant heat source under dry conditions (2) heated via radiant energy while half-submerged in flowing water at 23°C and (3) heated via convective transfer by increasing water temperature from 23°C to 35°C. Cooling was achieved in all treatments by removing the heat source and with C. porosushalf-submerged in flowing water at 23°C. In all treatments, the heart rate of C. porosus increased markedly in response to heating and decreased rapidly with the removal of the heat source. Heart rate during heating was significantly faster than during cooling at any given body temperature, i.e. there was a significant heart rate hysteresis. There were two identifiable responses to heating and cooling. During the initial stages of applying or removing the heat source, there was a dramatic increase or decrease in heart rate (`rapid response'), respectively, indicating a possible cardiac reflex. This rapid change in heart rate with only a small change or no change in body temperature (& .5°C) resulted in Q10 values greater than 4000, calling into question the usefulness of this measure on heart rate during the initial stages of heating and cooling. In the later phases of heating and cooling, heart rate changed with body temperature, with Q10 values of 2–3. The magnitude of the heart rate response differed between treatments, with radiant heating during submergence eliciting the smallest response. The heart rate of C. porosus outside of the`rapid response' periods was found to be a function of the heat load experienced at the animal surface, as well as on the mode of heat transfer. Heart rate increased or decreased rapidly when C. porosus experienced large positive (above 25 W) or negative (below –15 W) heat loads,respectively, in all treatments. For heat loads between –15 W and 20 W,the increase in heart rate was smaller for the `unnatural' heating by convection in water compared with either treatment using radiant heating. Our data indicate that changes in heart rate constitute a thermoregulatory mechanism that is modulated in response to the thermal environment occupied by the animal, but that heart rate during heating and cooling is, in part,controlled independently of body temperature.
Publisher: Oxford University Press (OUP)
Date: 2015
Publisher: Wiley
Date: 20-09-2008
Publisher: Elsevier BV
Date: 05-1992
Publisher: Elsevier BV
Date: 12-2009
DOI: 10.1016/J.CBPA.2009.09.001
Abstract: The green striped burrowing frog, Cyclorana alboguttata, spends, on average, nine to ten months of every year in aestivation. Recently, C. alboguttata has been the focus of much investigation regarding the physiological processes involved in aestivation, yet our understanding of this frog's capacity to metabolically depress remains limited. This study aimed to extend our current knowledge of metabolic depression during aestivation in C. alboguttata. C. alboguttata reduced whole animal metabolism by 82% within 5weeks of aestivation. The effects of aestivation on mass specific in vitro tissue metabolic rate (VO(2)) varied among in idual organs, with muscle and liver slices showing significant reductions in metabolism kidney VO(2) was elevated and there was no change in the VO(2) of small intestine tissue slices. Organ size was also affected by aestivation, with significant reductions in the mass of all tissues, except the gastrocnemius. These reductions in organ size, combined with changes in mass specific VO(2) of tissue slices, resulted in further energy savings to aestivating animals. This study shows that C. alboguttata is capable of selectively down- or up-regulating in idual tissues, using both changes in metabolic rate and morphology. This strategy allows maximal energy savings during aestivation without compromising organ functionality and survival at arousal.
Publisher: Wiley
Date: 19-07-2011
Publisher: The Company of Biologists
Date: 15-02-2021
DOI: 10.1242/JEB.242284
Publisher: Wiley
Date: 21-09-2021
DOI: 10.1002/JEZ.2412
Publisher: Elsevier BV
Date: 03-2007
DOI: 10.1016/J.CBPA.2006.12.023
Abstract: Connective tissue has recently been found to play a role in mediating mammalian skeletal muscle atrophy. We investigated connective tissue remodelling in the skeletal muscle of a species of the Australian burrowing frog, Cyclorana alboguttata. Despite being inactive whilst aestivating, the frog shows an inhibition of muscle atrophy. Connective tissue size and distribution was measured in histological sections of the cruralis muscle of control and aestivating C. alboguttata. Using a custom written software application we could detect no significant difference in any connective tissue morphological parameter between the two treatment groups. Biochemical measurements of gelatinase activity showed 2-fold higher activity in aestivating gastrocnemius muscle than in controls (p<0.001). We measured the messenger RNA transcript levels for C. alboguttata metalloproteinase 2 (MMP2) and tissue inhibitor of metalloproteinase 2 (TIMP2) in cruralis skeletal muscle using quantitative real-time PCR. The trend of reduced expression of the two genes in the aestivators did not meet statistical significance. This work indicates that aestivation in C. alboguttata leads to subtle and specific changes in some extracellular matrix remodelling factors. Their main impact is to maintain proportional representation of extracellular matrix components of skeletal muscle and therefore preserve the active frog phenotype.
Publisher: The Company of Biologists
Date: 09-2022
DOI: 10.1242/JEB.243924
Abstract: Determining the contribution of elevated ultraviolet-B radiation (UVBR 280–315 nm) to hibian population declines is being hindered by a lack of knowledge about how different acute UVBR exposure regimes during early life-history stages might affect post-metamorphic stages via long-term carryover effects. We acutely exposed tadpoles of the Australian green tree frog (Litoria caerulea) to a combination of different UVBR irradiances and doses in a multi-factorial laboratory experiment, and then reared them to metamorphosis in the absence of UVBR to assess carryover effects in subsequent juvenile frogs. Dose and irradiance of acute UVBR exposure influenced carryover effects into metamorphosis in somewhat opposing manners. Higher doses of UVBR exposure in larvae yielded improved rates of metamorphosis. However, exposure at a high irradiance resulted in frogs metamorphosing smaller in size and in poorer condition than frogs exposed to low and medium irradiance UVBR as larvae. We also demonstrate some of the first empirical evidence of UVBR-induced telomere shortening in vivo, which is one possible mechanism for life-history trade-offs impacting condition post-metamorphosis. These findings contribute to our understanding of how acute UVBR exposure regimes in early life affect later life-history stages, which has implications for how this stressor may shape population dynamics.
Publisher: Springer Science and Business Media LLC
Date: 07-11-2008
DOI: 10.1007/S00359-007-0284-0
Abstract: Despite prolonged immobility the desert frog, Cyclorana alboguttata, suffers little impairment in muscle function. To determine compensatory mechanisms at neuromuscular junctions, transmitter release was examined along primary terminals in C. alboguttata iliofibularis muscle. Using extracellular recording we found the litudes of evoked endplate currents were significantly smaller in dormant frogs. In active frogs we identified two negatively sloping proximal-distal gradients of transmitter frequency and quantal content a shallow proximal-distal gradient with low probability of transmitter release ( 0.6). During aestivation, only a shallow gradient was identified. The high probability release sites in control frogs were inhibited during aestivation by a mechanism that could be reversed by (1) increasing the extracellular calcium concentration, and (2) increasing the frequency of stimulation. This suggests that transmitter vesicles are available during aestivation but not released. We quantified expression of messenger RNA transcripts coding for the transmitter vesicle-docking proteins synaptotagmin 1, syntaxin 1B and UNC-13. All three were rare transcripts maintained at control values during aestivation. Neuromuscular remobilisation after dormancy in C. alboguttata is more likely a product of rapidly reversible physiologic mechanisms than reorganisations of the neuromuscular transcriptome.
Publisher: Elsevier BV
Date: 06-1992
Publisher: Springer Science and Business Media LLC
Date: 19-10-2006
DOI: 10.1007/S00360-005-0033-Z
Abstract: Changes in heart rate (f(H)) and cloacal ventilation frequency (f(C)) were investigated in the Fitzroy turtle, Rheodytes leukops, under normoxic (17.85 kPa) and hypoxic (3.79 kPa) conditions at 25 degrees C. Given R. leukops' high reliance on aquatic respiration via the cloacal bursae, the objective of this study was to examine the effect of varying aquatic PO(2) levels upon the expression of a bradycardia in a freely ing, bimodally respiring turtle. In normoxia, mean ing f(H) and f(C) for R. leukops remained constant with increasing submergence length, indicating that a bradycardia failed to develop during extended es of up to 3 days. Alternatively, exposure to aquatic hypoxia resulted in the expression of a bradycardia as recorded by a decreasing mean ing f(H) with increasing e duration. The observed bradycardia is attributed to a hypoxic-induced metabolic depression, possibly facilitated by a concurrent decrease in f(C). Results suggest that R. leukops alters its strategy from aquatic O(2) extraction via cloacal respiration in normoxia to O(2) conservation when exposed to aquatic hypoxia for the purpose of extending e duration. Upon surfacing, a significant tachycardia was observed for R. leukops regardless of aquatic PO(2), presumably functioning to rapidly equilibrate blood and tissue gas tensions with alveolar gas to reduce surfacing duration.
Publisher: The Company of Biologists
Date: 2021
DOI: 10.1242/JEB.242155
Publisher: The Royal Society
Date: 19-06-2012
Abstract: The emerging field of Conservation Physiology links environmental change and ecological success by the application of physiological theory, approaches and tools to elucidate and address conservation problems. Human activity has changed the natural environment to a point where the viability of many ecosystems is now under threat. There are already many descriptions of how changes in biological patterns are correlated with environmental changes. The next important step is to determine the causative relationship between environmental variability and biological systems. Physiology provides the mechanistic link between environmental change and ecological patterns. Physiological research, therefore, should be integrated into conservation to predict the biological consequences of human activity, and to identify those species or populations that are most vulnerable.
Publisher: Canadian Science Publishing
Date: 04-2003
DOI: 10.1139/Z03-037
Abstract: The objective of this study was to investigate how seasonally fluctuating environmental conditions influence the ing performance of the highly aquatic, bimodally respiring turtle Rheodytes leukops in a natural setting. Over four consecutive seasons (Austral autumn 2000 to summer 2001), the ing behaviour of adult turtles was recorded via pressure-sensitive timedepth recorders within Marlborough Creek, central Queensland, Australia. Short surfacing intervals recorded for R. leukops in winter suggest that the species utilizes aquatic respiration as an overwintering strategy to prevent the development of a metabolic acidosis during the long inactive es observed during the season. As water temperature increases and aquatic P O 2 decreases, R. leukops switches from facultative to obligate air-breathing, presumably because of the increased metabolic cost associated with aquatic respiration under summer conditions. Increases in mean surfacing time from winter to spring and summer are attributed to seasonal changes in behaviour possibly associated with foraging rather than to the physiological state of the turtle, given that no difference in median surfacing time among seasons was observed.
Publisher: Elsevier BV
Date: 06-2009
Publisher: Oxford University Press (OUP)
Date: 2016
Publisher: Wiley
Date: 15-08-1995
Publisher: Elsevier BV
Date: 06-2009
Publisher: Wiley
Date: 07-01-2010
Publisher: Springer Science and Business Media LLC
Date: 13-01-2005
DOI: 10.1007/S00359-004-0593-5
Abstract: This study examined the effect of prolonged inactivity, associated with aestivation, on neuromuscular transmission in the green-striped burrowing frog, Cyclorana alboguttata. We compared the structure and function of the neuromuscular junctions on the iliofibularis muscle from active C. alboguttata and from C. alboguttata that had been aestivating for 6 months. Despite the prolonged period of immobility, there was no significant difference in the shape of the terminals (primary, secondary or tertiary branches) or the length of primary terminal branches between aestivators and non-aestivators. Furthermore, there was no significant difference in the membrane potentials of muscle fibres or in miniature end plate potential (EPP) frequency and litude. However, there was a significant decrease in evoked transmitter release characterised by a 56% decrease in mean EPP litude, and a 29% increase in the failure rate of nerve terminal action potentials to evoke transmitter release. The impact of this suite of neuromuscular characteristics on the locomotor performance of emergent frogs is discussed.
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/MF12194
Abstract: The tagging of aquatic and semi-aquatic animals with acoustic transmitters and their detection by passive underwater receivers has gained huge popularity over the past decade. This technology offers researchers the opportunity to monitor the finite- to broad-scale movements of multiple in iduals over many years however, the sheer scale and spatial complexity of these datasets are often beyond the capabilities of routine database and spread-sheet applications. In the present paper, we describe software (V-Track) that greatly facilitates the assimilation, analysis and synthesis of animal-location data collected by underwater passive acoustic receivers. The principal features within V-Track are the behavioural event qualifier (BEQ) and the receiver-distance matrix (RDM) calculator. The BEQ identifies and catalogues horizontal movements from receiver detection data, or vertical movements from transmitter sensor data (depth or temperature). The RDM is generated from the geographical location of the acoustic receivers and is utilised by V-Track to illustrate the behavioural event information in a spatial context. V-Track is a package written within the R-programming language, and a graphical user interface is also provided. Here, we feature two case studies to demonstrate software functionality for defining and quantifying behaviour in acoustically tagged marine and freshwater vertebrates.
Publisher: Canadian Science Publishing
Date: 09-2003
DOI: 10.1139/Z03-153
Abstract: The purpose of this study was to determine whether a relationship existed between the diel surfacing trends of the bimodally respiring freshwater turtle Rheodytes leukops and daily fluctuations in specific biotic and abiotic factors. The diel surfacing behaviour of adult R. leukops was recorded over four consecutive seasons (Austral autumn 2000 summer 2001) within Marlborough Creek, central Queensland, Australia, using pressure-sensitive timedepth recorders. Additionally, diurnal variations in water temperature and aquatic PO 2 level, as well as the turtle's behavioural state (i.e., active versus resting), were monitored. In autumn and summer, surfacing frequency increased significantly during the daylight hours, with peak levels normally occurring around dawn (05000700) and dusk (17001900). However, no consistent diel surfacing trend was recorded for the turtles in winter or spring, owing to considerable variation among in idual R. leukops. Diurnal surfacing trends recorded for R. leukops in autumn and summer are attributed to periods of increased activity (possibly associated with foraging) during the daylight hours and not to daily variations in water temperature or aquatic PO 2 level. Turtles generally remained at a depth greater than 1 m throughout the day, where the effect of diel fluctuations in water temperature ( .5 °C) and aquatic PO 2 level ( mm Hg (1 mm Hg = 133.322 Pa)) was considered to be negligible.
Publisher: Elsevier BV
Date: 12-2005
DOI: 10.1016/J.CBPA.2005.09.013
Abstract: During aestivation, the gut of the green-striped burrowing frog, Cyclorana alboguttata undergoes significant morphological down-regulation. Despite the potential impact such changes might have on the re-feeding efficiency of these animals following aestivation, they appear to be as efficient at digesting their first meals as active, non-aestivating animals. Such efficiency might come about by the rapid restoration of intestinal morphology with both arousal from aestivation and the initial stages of re-feeding. Consequently, this study sought to determine what morphological changes to the intestine accompany arousal and re-feeding following 3 months of aestivation. Arousal from aestivation alone had a marked impact on many morphological parameters, including small and large intestine masses, small intestinal length, LF heights, enterocyte cross-sectional area and microvilli height and density. In addition, the onset of re-feeding was correlated with an immediate reversal of many morphological parameters affected by 3 months of aestivation. Those parameters that had not returned to control levels within 36 h of feeding generally had returned to control values by the completion of digestion (i.e. defecation of the meal). Re-feeding was also associated with several changes in enterocyte morphology including the incorporation in intracytoplasmic lipid droplets and the return of enterocyte nuclear material to the 'active' euchromatin state. In conclusion, morphological changes to the gut of aestivating frogs which occur during aestivation are transitory and rapidly reversible with both arousal from aestivation and re-feeding. The proximate causes behind these transitions and their functional significance are discussed.
Publisher: The Company of Biologists
Date: 2013
DOI: 10.1242/JEB.072827
Abstract: Preservation of muscle morphology depends on a continuing regulatory balance between molecules that protect, and molecules that damage, muscle structural integrity. Excessive disruption of the biochemical balance that favours reactive oxygen species (ROS) in disused muscles may lead to oxidative stress which in turn is associated with increased atrophic or apoptotic signalling and/or oxidative damage to the muscle and thus muscle disuse atrophy. Increases in rate of oxygen consumption likely increase the overall generation of ROS in vivo. Temperature-induced increases in muscle oxygen consumption rate occur in some muscles of ectotherms undergoing prolonged muscular disuse during aestivation. In the green-striped burrowing frog, Cyclorana alboguttata, both large jumping muscles and small non-jumping muscles undergo atrophy seemingly commensurate with their rate of oxygen consumption during aestivation. However, since the extent of atrophy in these muscles is not enhanced at higher temperatures despite a temperature sensitive rate of oxygen consumption in the jumping muscle, we proposed that muscles are protected by biochemical means that when mobilised at higher temperatures inhibit atrophy. We proposed the biochemical response to temperature would be muscle-specific. We examined the effect of temperature on the antioxidant and heat shock protein systems and evidence of oxidative damage to lipids and proteins in two functionally different skeletal muscles, gastrocnemius (jumping muscle) and iliofibularis (non-jumping muscle), by aestivating frogs at 24 and 30oC for six months. We assayed small molecule antioxidant capacity, mitochondrial and cytosolic SOD and Hsp70 to show that protective mechanisms in disused muscles are differentially regulated both with respect to temperature and aestivation. High aestivation temperature results in an antioxidant response in the metabolically temperature-sensitive jumping muscle. We assayed lipid peroxidation and protein oxidation to show that oxidative damage is apparent during aestivation and its pattern is muscle-specific, but unaffected by temperature. Consideration is given to how the complex responses of muscle biochemistry inform of the different strategies muscles may use in regulating their oxidative environment during extended disuse and disuse at high temperature.
Publisher: Wiley
Date: 07-2003
Publisher: Wiley
Date: 09-02-2017
Publisher: Springer Science and Business Media LLC
Date: 1990
DOI: 10.1007/BF00004433
Publisher: Elsevier BV
Date: 10-2018
Publisher: Society for the Study of Amphibians and Reptiles
Date: 03-2013
DOI: 10.1670/11-160
Publisher: Springer Science and Business Media LLC
Date: 02-2002
DOI: 10.1007/S00360-001-0242-Z
Abstract: The Green-striped burrowing frog, Cyclorana alboguttata survives extended drought periods by burrowing underground and aestivating. These frogs remain immobile within cocoons of shed skin and mucus during aestivation and emerge from their burrows upon heavy rains to feed and reproduce. Extended periods of immobilisation in mammals typically result in muscle atrophy and a decrease in muscle performance. We examined the effect of aestivation and hence prolonged immobilisation, on skeletal muscle mass, in vitro muscle performance, and locomotor performance in C. alboguttata. Frogs were aestivated in soil for 3 months and were compared with control animals that remained active, were fed, and had a continual supply of water. Compared to the controls, the wet mass of the gastrocnemius, sartorius, gracilus major, semimembranosus, peroneus, extensor cruris, tibialis posticus and tibialis anticus longus of aestivators remained unchanged indicating no muscle atrophy. The in-vitro performance characteristics of the gastrocnemius muscle were maintained and burst swimming speed was unaffected, requiring no recovery from the extended period of immobilisation associated with aestivation. This preservation of muscle size, contractile condition and locomotor performance through aestivation enables C. alboguttata to compress their life history into unpredictable windows of opportunity, whenever heavy rains occur.
Publisher: The Royal Society
Date: 10-2022
Abstract: Anthropogenic ozone depletion has led to a 2–5% increase in ultraviolet B radiation (UVBR) levels reaching the earth's surface. Exposure to UVBR causes harmful DNA damage in hibians, but this is minimized by DNA repair enzymes such as thermally sensitive cyclobutane pyrimidine dimer (CPD)-photolyase, with cool temperatures slowing repair rates. It is unknown whether hibian species differ in the repair response to a given dose of UVBR across temperatures. We reared larvae of three species ( Limnodynastes peronii , Limnodynastes tasmaniensis and Platyplectrum ornatum ) at 25°C and acutely exposed them to 80 µW cm −2 UVBR for 2 h at either 20°C or 30°C. UVBR-mediated DNA damage was measured as larvae repaired damage in photoreactive light at their exposure temperatures. Cool temperatures increased DNA damage in two species and slowed DNA repair rate in P. ornatum . The magnitude of DNA damage incurred from UVBR was species-specific. Platyplectrum ornatum had the lowest CPDs and DNA repair rates, and the depressive effects of low temperature on photorepair were greater in L. tasmaniensis . Considering the susceptibility of most aquatic organisms to UVBR, this research highlighted a need to consider the complexity of species-specific physiology when forecasting the influence of changing UVBR and temperature in aquatic ecosystems.
Publisher: Wiley
Date: 02-2004
Publisher: Wiley
Date: 11-1993
Abstract: Methyl methacrylate corrosion casts were made of the blood-vascular system of the lingual salt glands of the estuarine crocodile, Crocodylus porosus, and examined with light and scanning electron microscopy. The 28-40 in idual salt glands, each opening separately via a single pore onto the dorsal surface of the tongue, are supplied by a pair of lingual arteries. Each gland is richly vascularized and is composed of 14-20 lobular sub-units, each having a dense network of capillaries. The blood flow in each gland is from the centre to its periphery, opposite to the direction of the flow of secretions in the ducts of the gland. The main collecting duct leading from the gland to the external pore was well vascularized. The blood supply to the glands of juvenile crocodiles raised in 20‰ salt water was more dense than in freshwater and, from cast masses, had a three-fold greater vascular volume. This study provides the first evidence which shows that the salt glands of crocodiles are morphologically labile and can adapt to the environmental salinity. © 1993 Wiley-Liss, Inc.
Publisher: Routledge
Date: 11-01-2023
Publisher: Elsevier BV
Date: 06-2009
Publisher: Public Library of Science (PLoS)
Date: 05-2013
Publisher: Canadian Science Publishing
Date: 06-1993
DOI: 10.1139/Z93-169
Abstract: Coronary arterial blood flow and pressure, intraventricular blood pressure, and ventral aortic blood velocity were measured in two anaesthetized school sharks (Galeorhinus australis) in order to examine the phasic relationships between these flows and pressures. Maximum instantaneous flow recorded in the ventral coronary artery was 0.37 mL∙min −1 ∙kg −1 body mass (estimated 0.63 mL∙min −1 ∙g −1 ventricular mass). The average mean coronary blood flow was estimated as 0.28 mL∙min −1 ∙g −1 ventricular mass during periods of high coronary blood flow. On average, 86% of coronary flow occurred during diastole. Coronary arterial flow began during the last quarter of ventricular systole. Coronary blood flow peaked when intraventricular pressure fell to just below zero immediately after ventricular systole. Coronary blood flow fell slightly as diastole continued and reflected the small fall in coronary arterial pressure. Coronary flow reversed briefly during isovolumic ventricular contraction. Increases in the proportion of the cardiac cycle occupied by ventricular diastole, which occur during hypoxic bradycardia, have the potential to more than double coronary blood flow provided coronary arterial pressure is maintained.
Publisher: Elsevier BV
Date: 06-2009
Publisher: Wiley
Date: 19-12-2015
Publisher: Elsevier BV
Date: 06-1999
Publisher: Oxford University Press (OUP)
Date: 2016
Publisher: The Royal Society
Date: 28-04-2005
Abstract: Specialization to a particular environment is one of the main factors used to explain species distributions. Antarctic fishes are often cited as a classic ex le to illustrate the specialization process and are regarded as the archetypal stenotherms. Here we show that the Antarctic fish Pagothenia borchgrevinki has retained the capacity to compensate for chronic temperature change. By displaying astounding plasticity in cardiovascular response and metabolic control, the fishes maintained locomotory performance at elevated temperatures. Our falsification of the specialization paradigm indicates that the effect of climate change on species distribution and extinction may be overestimated by current models of global warming.
Publisher: Springer Science and Business Media LLC
Date: 28-03-2008
DOI: 10.1007/S00360-008-0261-0
Abstract: Green-striped burrowing frogs, Cyclorana alboguttata, survive droughts by entering a metabolic depression called aestivation, characterised by a reduction in resting oxygen consumption by 80%. Aestivation in C. alboguttata is manifest by transcriptional silencing of skeletal muscle bioenergetic genes, such as NADH ubiquinone oxidoreductase 1, ATP synthase and superoxide dismutase 2. In this study, we hypothesised that aestivation is associated with epigenetic change in frog muscle. We assessed mRNA transcript abundance of seven genes that code for proteins with established roles in epigenetically-mediated gene silencing [transcriptional co-repressor SIN3A, DNA (cytosine-5-) methyltransferase 1, methyl CpG binding protein 2, chromodomain helicase DNA binding protein 4, histone binding protein rbbp4, histone deacetylase 1 and nuclear receptor co-repressor 2] using qRT-PCR. These seven genes showed a modest (1.1-3.5-fold) but coordinated upregulation in 6-month aestivating muscle. This reached significance for SIN3A and DNA cytosine-5-methyltransferase 1 in standard pair-wise comparisons (p < 0.05), and the candidates as a whole when analysed by Fisher's combined probability test (p < 0.01). These data are consistent with the hypothesis that the transcriptional silencing and metabolic depression that occurs during seasonal dormancy are associated with chromatin remodelling, and present a novel ex le of an environmentally induced epigenetic modification in an adult vertebrate.
Publisher: Springer Science and Business Media LLC
Date: 04-1992
DOI: 10.1007/BF00357532
Publisher: Inter-Research Science Center
Date: 09-03-2015
DOI: 10.3354/DAO02825
Abstract: The dugong Dugong dugon is classified as Vulnerable to extinction but may be endangered in some regions. Cause of death in stranded dugongs has not been determined in a large proportion of animals examined, with investigations hindered by limited information on dugong health and diseases, and paucity of knowledge of common or endemic pathological findings. Here we describe pathological findings in harvested dugongs from the relatively pristine area of central Torres Strait, and we characterise lesions attributable to drowning. Other recorded lesions were mild and predominated by host reaction to the presence of trematodes within the gastrointestinal tracts, liver and pancreas. Ascarid worm burdens were low in comparison to dugongs from developed coastlines. Hepatocellular lipofuscin and ferritin pigmentation were commonly observed, more pronounced in livers of older animals and concurrent with periportal and bridging fibrosis. Lesions attributable to drowning included incomplete collapse of lungs, dorsal or diffuse pulmonary congestion, mild intra-alveolar haemorrhage and oedema, mild interstitial oedema and rupture of peripheral alveolar septae with acute myofibre fragmentation and degeneration. No accumulation of foam or aspiration of water or particulate matter was observed, suggesting that dugongs 'dry drown'. Morphometric features of normal spleen are also presented. Characterisation of common pathological findings and those attributable to drowning in this species will aid in the interpretation of post mortem findings for the significant number of dugongs found deceased along urbanised coastlines.
Publisher: American Physiological Society
Date: 03-2006
DOI: 10.1152/AJPREGU.00380.2005
Abstract: Long (6- to 9-mo) bouts of estivation in green-striped burrowing frogs lead to 28% atrophy of cruralis oxidative fibers ( P 0.05) and some impairment of in vitro gastrocnemius endurance ( P 0.05) but no significant deficit in maximal twitch force production. These data suggest the preferential atrophy of oxidative fibers at a rate slower than, but comparable to, laboratory disuse models. We tested the hypothesis that the frog limits atrophy by modulating oxidative stress. We assayed various proteins at the transcript level and verified these results for antioxidant enzymes at the biochemical level. Transcript data for NADH ubiquinone oxidoreductase subunit 1 (71% downregulated, P 0.05) and ATP synthase (67% downregulated, P 0.05) are consistent with mitochondrial quiescence and reduced oxidant production. Meanwhile, uncoupling protein type 2 transcription ( P = 0.31), which is thought to reduce mitochondrial leakage of reactive oxygen species, was maintained. Total antioxidant defense of water-soluble (22.3 ± 1.7 and 23.8 ± 1.5 μM/μg total protein in control and estivator, respectively, P = 0.53) and membrane-bound proteins (31.5 ± 1.9 and 42.1 ± 7.3 μM/μg total protein in control and estivator, respectively, P = 0.18) was maintained, equivalent to a bolstering of defense relative to oxygen insult. This probably decelerates muscle atrophy by preventing accumulation of oxidative damage in static protein reserves. Transcripts of the mitochondrially encoded antioxidant superoxide dismutase type 2 (67% downregulated, P 0.05) paralleled mitochondrial activity, whereas nuclear-encoded catalase and glutathione peroxidase were maintained at control values ( P = 0.42 and P = 0.231), suggesting a dissonance between mitochondrial and nuclear antioxidant expression. Pyruvate dehydrogenase kinase 4 transcription was fourfold lower in estivators ( P = 0.11), implying that, in contrast to mammalian hibernators, this enzyme does not drive the combustion of lipids that helps spare hypometabolic muscle.
Publisher: Elsevier BV
Date: 04-2007
Publisher: Springer Science and Business Media LLC
Date: 31-08-2004
DOI: 10.1007/S00360-004-0446-0
Abstract: Reptiles change heart rate and blood flow patterns in response to heating and cooling, thereby decreasing the behavioural cost of thermoregulation. We tested the hypothesis that locally produced vasoactive substances, nitric oxide and prostaglandins, mediate the cardiovascular response of reptiles to heat. Heart rate and blood pressure were measured in eight crocodiles (Crocodylus porosus) during heating and cooling and while sequentially inhibiting nitric-oxide synthase and cyclooxygenase enzymes. Heart rate and blood pressure were significantly higher during heating than during cooling in all treatments. Power spectral density of heart rate and blood pressure increased significantly during heating and cooling compared to the preceding period of thermal equilibrium. Spectral density of heart rate in the high frequency band (0.19-0.70 Hz) was significantly greater during cooling in the saline treatment compared to when nitric-oxide synthase and cyclooxygenase enzymes were inhibited. Cross spectral analysis showed that changes in blood pressure preceded heart rate changes at low frequencies (< 0.1 Hz) only. We conclude that the autonomic nervous system controls heart rate independently from blood pressure at higher frequencies while blood pressure changes determine heart rate at lower frequencies. Nitric oxide and prostaglandins do not control the characteristic heart rate hysteresis response to heat in C. porosus, although nitric oxide was important in buffering blood pressure against changes in heart rate during cooling, and inhibition caused a compensatory decrease in parasympathetic stimulation of the heart.
Publisher: The Company of Biologists
Date: 10-2017
DOI: 10.1242/JEB.155440
Abstract: Survival of air-breathing, ing ectotherms is dependent on their capacity to optimise the time available for obligate underwater activities, such as predator avoidance. Submergence times are thermally sensitive, with e durations significantly reduced by increases in water temperature, deeming these animals particularly vulnerable to the effects of climate change. The physiological mechanisms underlying this compromised performance are unclear but are hypothesised to be linked to increased oxygen demand and a reduced capacity for metabolic depression at elevated temperatures. Here, we investigated how water temperature (both acute and chronic exposures) affected the physiology of juvenile estuarine crocodiles (Crocodylus porosus) performing predator avoidance es (i.e. fright- es). Diving oxygen consumption, ‘fright’ bradycardia, haematocrit and haemoglobin (indicators of blood oxygen carrying capacity) were assessed at two test temperatures, reflective of different climate change scenarios (i.e. current summer water temperatures, 28°C, and ‘high’ climate warming, 34°C). Diving oxygen consumption rate increased threefold between 28 and 34°C (Q10=7.4). The capacity to depress oxygen demand was reduced at elevated temperatures, with animals lowering oxygen demand from surface levels by 52.9±27.8% and 27.8±16.5% (means±s.e.m.) at 28°C and 34°C, respectively. Resting and post-fright- e haematocrit and haemoglobin were thermally insensitive. Together these findings suggest decrements in fright- e performance at elevated temperatures stem from increased oxygen demand coupled with a reduced capacity for metabolic depression.
Publisher: Elsevier BV
Date: 02-2010
DOI: 10.1016/J.CBPA.2009.10.032
Abstract: In fish, exposure to waters of low pH causes significant damage to the gill resulting in fatal iono- and osmoregulatory disturbance. In hibians, exposure to acid waters also disrupts ionic homeostasis, however the extent and nature of injuries to hibian larvae from acid exposure are poorly understood. Changes in gross morphology and ultrastructure of the gills and integument were examined, together with measures of Na(+) efflux/uptake, in larval Litoria fallax (Amphibia: Anura) following acute acid exposure. Examination of tissues revealed significant changes in morphology and ultrastructure of both gills and the integument following acutely lethal exposure to low pH water. Changes to the gills of acid-exposed L. fallax larvae included lifting of the branchial epithelium and opening of tight junctions between pavement cells (with a consequent reduction in tight junction length). Damage to epithelial cell-cell tight junctions was also apparent at the integument along with widespread oncosis and localised epithelial necrosis. Mucous secretory activity at the gills and body surface was largely unaffected by acid exposure, with little or no difference in density, cross-sectional area and number of epithelial mucous secretory vesicles in acid-exposed and control larvae. Changes in morphology and ultrastructure at low pH were accompanied by significant Na(+) loss (up to 50% of the total body Na(+) content) attributable in large part to increased paracellular ionic efflux across the gills as well as increased transcellular and paracellular efflux of ions across the integument.
Publisher: Oxford University Press (OUP)
Date: 2023
Abstract: Increasing drought frequency and duration pose a significant threat to fish species in dryland river systems. As ectotherms, fish thermal and hypoxia tolerances directly determine the capacity of species to persist in these environments during low flow periods when water temperatures are high and waterbodies become highly stratified. Chronic thermal stress can compound the impacts of acute hypoxic events on fish resulting in significant fish mortality however, it is not known if all size classes are equally susceptible, or if the allometric scaling of physiological processes means some size classes are disproportionately affected. We investigated the physiological responses of Murray cod (Maccullochella peelii) over a four-fold body size range (0.2–3000 g) to acute changes in water temperature and oxygen concentration following 4 weeks of acclimation to representative spring (20°C) and summer (28°C) water temperatures. We recorded maximum thermal tolerance (CTmax), oxygen limited thermal tolerance (PCTmax), lowest tolerable oxygen level (as the oxygen level at which lose equilibrium O2,LOE), gill ventilation rates and aerial surface respiration threshold, blood oxygen transport capacity and lactate accumulation. Acclimation to elevated water temperatures improved thermal and hypoxia tolerance metrics across all size classes. However, body size significantly affected thermal and hypoxia responses. Small M. peelii were significantly less hypoxia tolerant than larger in iduals, while larger fish were significantly less thermal tolerant than smaller fish. Hypoxia constrained thermal tolerance in M. peelii, with both small and large fish disproportionally compromised relative to mid-sized fish. Our findings indicate that both very small/young (larvae, fry, fingerlings) and very large/older M. peelii in dryland rivers are at significant risk from the combined impacts of a warming and drying climate and water extraction. These data will inform policy decisions that serve to balance competing demands on precious freshwater resources.
Publisher: Oxford University Press (OUP)
Date: 30-10-2021
Abstract: Examining the social behaviors of solitary species can be challenging due to the rarity in which interactions occur and the large and often inaccessible areas which these animals inhabit. As shared space-use is a prerequisite for the expression of social behaviors, we can gain insights into the social environments of solitary species by examining the degree of spatial overlap between in iduals. Over a 10-year period, we examined how spatial overlap amongst 105 estuarine crocodiles Crocodylus porosus was influenced by season, sex, and movement tactic. We discovered that crocodiles displayed highly consistent spatial overlaps with conspecifics between months and across years. Furthermore, male crocodiles that exhibited a greater degree of site fidelity displayed more stable social environments, while females and males that were less site-attached had more dynamic social environments with spatial overlaps between conspecifics peaking during the mating season. Our results demonstrate how long-term tracking of multiple in iduals within the same population can be used to quantify the spatial structure and social environment of cryptic and solitary species.
Publisher: Canadian Science Publishing
Date: 06-1992
DOI: 10.1139/Z92-167
Abstract: An in situ heart preparation perfused with oxygenated saline was used to examine cardiac performance at 25 °C in yellowfin tuna (Thunnus albacares) and skipjack tuna (Katsuwonus pelamis). Heart rates (91–172 bpm in skipjack tuna and 101–157 bpm in yellowfin tuna) were comparable to those measured in vivo, and physiological stroke volumes were possible in yellowfin tuna with subambient filling pressures. In yellowfin tuna, maximum stroke volume and cardiac output were similar to the values obtained in vivo with spinally blocked animals mean output pressures (up to 145 cmH 2 O, 1 cmH 2 O = 0.098 kPa) could exceed in vivo values without a major decrease in the resting cardiac output (homeometric regulation). In contrast, saline-perfused skipjack tuna hearts could not develop physiological output pressures without compromising cardiac output, with cardiac output being only 63% of the in vivo value at an output pressure near the in vivo ventral aortic pressure. The poor performance of the skipjack tuna heart is attributed to limited oxygen diffusion through the thicker walled ventricle. We conclude that the tuna heart is more dependent on its coronary circulation for normal function than the hearts of other fishes examined thus far. The coronary circulation was perfused with saline at various flow rates in isolated hearts from skipjack tuna to develop a pressure–flow relationship for the intact circulation. Coronary resistance reached a minimum of 24 cmH 2 O∙min∙g ventricular mass/mL at a flow rate of 2 mL/(min∙g ventricular mass) with perfusion pressure about 40 cmH 2 O. In vivo coronary blood flow was estimated from the pressure–flow relationship as 0.67 mL/(min∙g ventricular mass). Injections of adrenaline, noradrenaline, and phenylephrine into coronary circulation under constant flow conditions increased perfusion pressure, indicating the possibility of α-adrenergic vasoconstriction.
Publisher: Elsevier BV
Date: 04-2007
Publisher: Elsevier BV
Date: 10-2005
DOI: 10.1016/J.YGCEN.2005.04.013
Abstract: The present study has examined expression and circulating levels of C-type natriuretic peptide (CNP) in the euryhaline bull shark, Carcharhinus leucas. Complementary DNA and deduced amino acid sequence for CNP in C. leucas were determined by RACE methods. Homology of CNP amino acid sequence in C. leucas was high both for proCNP and for mature CNP when compared with previously identified elasmobranch CNPs. Mature CNP sequence in C. leucas was identical to that in Triakis scyllia and Scyliorhinus canicula. Levels of expression of CNP mRNA were significantly decreased in the atrium but did not change in either the brain or ventricle following acclimation to a SW environment. However, circulating levels of CNP significantly increased from 86.0+/-7.9 fmol ml(-1) in FW to 144.9+/-19.5 fmol ml(-1) in SW. The results presented demonstrate that changes in environmental salinity influences both synthesis of CNP from the heart and also circulating levels in C. leucas. Potential stimulus for release and modes of action are discussed.
Publisher: Canadian Science Publishing
Date: 08-2013
Abstract: Cardiovascular adaptations that permit successful exploitation of polar marine waters by fish requires a capacity to negate or compensate for the depressive effects of low temperatures on physiological processes. Here, we examined the effects of acute and chronic temperature change on the maximum cardiac performance of shorthorn sculpin (Myoxocephalus scorpius (L., 1758)) captured above the Arctic Circle. Our aim was to establish if the sculpin’s success at low temperatures was achieved through thermal independence of cardiac function or via thermal compensation as a result of acclimation. Maximum cardiac performance was assessed at both 1 and 6 °C with a working perfused heart preparation that was obtained after fish had been acclimated to either 1 or 6 °C. Thus, tests were performed at the fish’s acclimation temperature and with an acute temperature change. Maximum cardiac output, which was relatively large ( mL·min −1 ·kg −1 body mass) for a benthic fish at a frigid temperature, was found to be independent of both acclimation temperature and test temperature. While maximum β-adrenergic stimulation produced positive chronotropy at both acclimation temperatures, inotropic effects were weak or absent. We conclude that thermal independence of cardiac performance at low temperature likely facilitated the exploitation of polar waters by the shorthorn sculpin.
Publisher: The Company of Biologists
Date: 2015
DOI: 10.1242/JEB.123166
Abstract: Daily thermal fluctuations (DTF) impact the capacity of ectotherms to maintain performance and energetic demands due to thermodynamic effects on physiological processes. Mechanisms which reduce the thermal sensitivity of physiological traits may buffer ectotherms from the consequences of DTF. Species which experience varying degrees of DTF in their environments may differ in their responses to thermally variable conditions, if thermal performance curves reflect environmental conditions. We tested the hypothesis that in response to DTF tadpoles from habitats characterised by small DTF would show greater plasticity in the thermal sensitivity physiological processes than tadpoles from environments characterised by large DTF. We tested the thermal sensitivity of physiological traits in tadpoles of three species which differ naturally in their exposure to DTF raised in control (24°C) and DTF treatments (20-30°C and 18-38°C). DTF reduced growth in all species. Development of tadpoles experiencing DTF was increased for tadpoles from highly thermally variable habitats (∼15%), and slower in tadpoles from less thermally variable habitats (∼30%). In general, tadpoles were unable to alter the thermal sensitivity of physiological processes, although DTF induced plasticity in metabolic enzyme activity in all species, although to a greater extent in species from less thermally variable environments. DTF increased upper thermal limits in all species (between 0.89-1.6°C). Our results suggest that the impact of increased thermal variability may favour some species while others are negatively impacted. Species that cannot compensate for increased variability by buffering growth and development will likely be most affected.
Publisher: Herpetologists League
Date: 12-2013
Publisher: The Company of Biologists
Date: 15-05-2020
DOI: 10.1242/JEB.229294
Publisher: Wiley
Date: 2005
Publisher: Wiley
Date: 05-2023
DOI: 10.1111/GCB.16726
Abstract: Ecological carryover effects, or delayed effects of the environment on an organism's phenotype, are central predictors of in idual fitness and a key issue in conservation biology. Climate change imposes increasingly variable environmental conditions that may be challenging to early life‐history stages in animals with complex life histories, leading to detrimental physiological and fitness effects in later life. Yet, the latent nature of carryover effects, combined with the long temporal scales over which they can manifest, means that this phenomenon remains understudied and is often overlooked in short‐term studies limited to single life‐history stages. Herein, we review evidence for the physiological carryover effects induced by elevated ultraviolet radiation (UVR 280–400 nm) as a potential contributor to recent hibian population declines. UVR exposure causes a suite of molecular, cellular and physiological consequences known to underpin carryover effects in other taxa, but there is a lack of research linking embryonic and larval UVR exposures to fitness consequences post‐metamorphosis in hibians. We propose that the key impacts of UVR on disease‐related hibian declines are facilitated through carryover effects that bridge embryonic and larval UVR exposure with potential increased disease susceptibility post‐metamorphosis. We conclude by identifying a practical direction for the study of ecological carryover effects in hibians that could guide future ecological research in the broader field of conservation physiology. Only by addressing carryover effects can many of the mechanistic links between environmental change and population declines be elucidated.
Publisher: Wiley
Date: 27-06-2023
DOI: 10.1111/GCB.16848
Abstract: Ultraviolet radiation (UVR) from the sun is a natural daytime stressor for vertebrates in both terrestrial and aquatic ecosystems. UVR effects on the physiology of vertebrates manifest at the cellular level, but have bottom‐up effects at the tissue level and on whole‐animal performance and behaviours. Climate change and habitat loss (i.e. loss of shelter from UVR) could interact with and exacerbate the genotoxic and cytotoxic impacts of UVR on vertebrates. Therefore, it is important to understand the range and magnitude of effects that UVR can have on a ersity of physiological metrics, and how these may be shaped by taxa, life stage or geographical range in the major vertebrate groups. Using a meta‐analytical approach, we used 895 observations from 47 different vertebrate species (fish, hibian, reptile and bird), and 51 physiological metrics (i.e. cellular, tissue and whole‐animal metrics), across 73 independent studies, to elucidate the general patterns of UVR effects on vertebrate physiology. We found that while UVR's impacts on vertebrates are generally negative, fish and hibians were the most susceptible taxa, adult and larvae were the most susceptible life stages, and animals inhabiting temperate and tropical latitudes were the most susceptible to UVR stress. This information is critical to further our understanding of the adaptive capacity of vulnerable taxon to UVR stress, and the wide‐spread sublethal physiological effects of UVR on vertebrates, such as DNA damage and cellular stress, which may translate up to impaired growth and locomotor performance. These impairments to in idual fitness highlighted by our study may potentially cause disruptions at the ecosystem scale, especially if the effects of this pervasive diurnal stressor are exacerbated by climate change and reduced refuge due to habitat loss and degradation. Therefore, conservation of habitats that provide refuge to UVR stress will be critical to mitigate stress from this pervasive daytime stressor.
Publisher: American Physiological Society
Date: 10-2017
DOI: 10.1152/AJPREGU.00067.2017
Abstract: Long-term studies have found that low-carbohydrate diets are more effective for weight loss than calorie-restricted diets in the short term but equally or only marginally more effective in the long term. Low-carbohydrate diets have been linked to reduced glycogen stores and increased feelings of fatigue. We propose that reduced physical activity in response to lowered glycogen explains the diminishing weight loss advantage of low-carbohydrate compared with low-calorie diets over longer time periods. We explored this possibility by feeding adult Drosophila melanogaster a standard or a low-carbohydrate diet for 9 days and measured changes in metabolic rate, glycogen stores, activity, and body mass. We hypothesized that a low-carbohydrate diet would cause a reduction in glycogen stores, which recover over time, a reduction in physical activity, and an increase in resting metabolic rate. The low-carbohydrate diet reduced glycogen stores, which recovered over time. Activity was unaffected by diet, but metabolic rate was reduced, in the low-carbohydrate group. We conclude that metabolic depression could explain the decreased effectiveness of low-carbohydrate diets over time and recommend further investigation of long-term metabolic effects of dietary interventions and a greater focus on physiological plasticity within the study of human nutrition.
Publisher: The Company of Biologists
Date: 03-2007
DOI: 10.1242/JEB.02711
Abstract: Prolonged immobilisation or unloading of skeletal muscle causes muscle disuse atrophy, which is characterised by a reduction in muscle cross-sectional area and compromised locomotory function. Animals that enter seasonal dormancy, such as hibernators and aestivators, provide an interesting model for investigating atrophy associated with disuse. Previous research on the hibian aestivator Cyclorana alboguttata (Günther 1867)demonstrated an absence of muscle disuse atrophy after 3 months of aestivation, as measured by gastrocnemius muscle contractile properties and locomotor performance. In this study, we aimed to investigate the effect of aestivation on iliofibularis and sartorius muscle morphology and contractile function of C. alboguttata over a longer, more ecologically relevant time-frame of 9 months. We found that whole muscle mass, muscle cross-sectional area, fibre number and proportions of fibre types remained unchanged after prolonged disuse. There was a significant reduction in iliofibularis fibre cross-sectional area (declined by 36% for oxidative fibre area and 39% for glycolytic fibre area) and sartorius fibre density (declined by 44%). Prolonged aestivation had little effect on the isometric properties of the skeletal muscle of C. alboguttata. There was a significant reduction in the isometric contraction times of the relatively slow-twitch iliofibularis muscle, suggesting that the muscle was becoming slower after 9 months of aestivation (time to peak twitch increased by 25%, time from peak twitch to half relaxation increased by 34% and time from last stimulus to half tetanus relation increased by 20%). However, the results of the work-loop analysis clearly demonstrate that, despite changes to muscle morphology and isometric kinetics, the overall contractile performance and power output levels of muscles from 9-month aestivating C. alboguttata are maintained at control levels.
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/MF09194
Abstract: Acrochordus arafurae is a fully aquatic, freshwater snake distributed throughout tropical Australia. To better understand the ecological factors influencing their behavioural repertoire, we remotely monitored field body temperature and ing in snakes free-ranging within their natural habitat. The body temperatures of A. arafurae exhibited a diel profile similar to the surface water temperature, and reflected the high proportion of time that snakes remained m from the surface. The average e depth was 0.62 m and 95% of es had an average depth of 1 m or less. Snakes occasionally ventured into deeper water ( m), and there was a positive correlation between e depth and duration. Average e duration was 6.6 min and 84% of es were terminated within 10 min, but all snakes performed es min during the 14-day observation period. We hypothesise that the e behaviour was strongly influenced by predation pressure. The snakes partake in short es within the aerobic e limit to reduce the amount of time they need to spend at the surface on each breathing bout, reducing the risk of predation by birds. Predation is a strong selective force that might alter the time allocation during e cycles.
Publisher: Springer Science and Business Media LLC
Date: 03-04-2010
DOI: 10.1007/S00360-010-0471-0
Abstract: Green-striped burrowing frogs (Cyclorana alboguttata) can depress their resting metabolism by more than 80% during aestivation. Previous studies have shown that this species is able to withstand long periods of immobilisation during aestivation while apparently maintaining whole muscle mass and contractile performance. The aim of this study was to determine the effect of prolonged aestivation on the levels of metabolic enzymes (CCO, LDH and CS) in functionally distinct skeletal muscles (cruralis, gastrocnemius, sartorius, iliofibularis and rectus abdominus) and liver of C. alboguttata. CS activity was significantly reduced in all tissues except for the cruralis, gastrocnemius and the liver. LDH activity was significantly reduced in the sartorius and rectus abdominus, but remained at control (active) levels in the other tissues. CCO activity was significantly reduced in the gastrocnemius and rectus abdominus, and unchanged in the remaining tissues. Muscle protein was significantly reduced in the sartorius and iliofibularis during aestivation, and unchanged in the remaining muscles. The results suggest that the energy pathways involved in the production and consumption of ATP are remodelled during prolonged aestivation but selective. Remodelling and subsequent down-regulation of metabolic activity seem to target the smaller non-jumping muscles, while the jumping muscles retain enzyme activities at control levels during aestivation. These results suggest a mechanism by which aestivating C. alboguttata are able to maintain metabolic depression while ensuring that the functional capacity of critical muscles is not compromised upon emergence from aestivation.
Publisher: The Company of Biologists
Date: 22-01-2004
DOI: 10.1242/JEB.00787
Abstract: The green-striped burrowing frog, Cyclorana alboguttata, survives extended drought periods by burrowing underground and aestivating. These frogs remain immobile within cocoons of shed skin and mucus during aestivation and emerge from their burrows upon heavy rains to feed and reproduce. Extended periods of immobilisation in mammals typically result in bone remodelling and a decrease in bone strength. We examined the effect of aestivation and, hence,prolonged immobilisation on cross-sectional area, histology and bending strength in the femur and tibiofibula of C. alboguttata. Frogs were aestivated in soil for three and nine months and were compared with control animals that remained active, were fed and had a continual supply of water. Compared with the controls, long bone size, anatomy and bending strength remained unchanged, indicating an absence of disuse osteoporosis. This preservation of bone tissue properties enables C. alboguttata to compress the active portions of their life history into unpredictable windows of opportunity, whenever heavy rains occur.
Publisher: Elsevier BV
Date: 07-2004
Publisher: The Company of Biologists
Date: 06-2011
DOI: 10.1242/JEB.054478
Abstract: Human-induced climate change is predicted to affect not only the mean temperature of the environment but also the variability and frequency of extreme climatic events. Variability in an organism's developmental environment has the potential to markedly affect an in idual's growth trajectory and physiological function, leading to impacts on in idual fitness and population dynamics. Thus, it is important to consider the consequences of thermal variability on developing organisms and understand their capacity to respond to such increased variation. We investigated the capacity of larval striped marsh frogs (Limnodynastes peronii) to initiate a response to increases in the thermal variability of their developmental environment by reducing the sensitivity of their physiological rate functions to changes in temperature. In variable environments, we expected the thermal sensitivity of rate functions to decrease and their performance breadth to widen so as to buffer the effect of thermal variability. We raised larvae in stable (24°C), narrowly variable (22–26°C mean 24°C) and widely variable (14–34°C mean 24°C) thermal environments and measured the thermal sensitivity of their locomotor performance, heart rate, oxygen consumption and activities of two metabolic enzymes, lactate dehydrogenase and cytochrome c oxidase. We found that the temperature-dependent relationships of these physiological functions did not differ between tadpoles raised in stable or variable thermal conditions. Furthermore, the Q10 values of each response variable were virtually unaffected by treatment when measured over the entire thermal range. Our results reveal that larval hibians exhibit little plasticity in metabolic traits to thermal variability. This lack of plasticity may have important implications for the growth and population dynamics of organisms in environments that are beginning to experience increased thermal variability.
Publisher: Public Library of Science (PLoS)
Date: 26-09-2007
Publisher: Elsevier BV
Date: 07-2015
DOI: 10.1016/J.CBPA.2015.04.001
Abstract: While there is a considerable body of work describing osmoregulation by elasmobranchs in brackish and saltwater, far fewer studies have investigated osmoregulation in hypersaline waters. We examined osmo- and ionoregulatory function and plasticity in juvenile brown-banded bamboo sharks, Chiloscyllium punctatum, exposed to three experimental salinities (25, 34 and 40‰) for two weeks. C. punctatum inhabits sheltered coastal areas and bays which can naturally become hypersaline as a consequence of evaporation of water but can also become hyposaline during flood events. We hypothesised that C. punctatum would demonstrate a phenotypically plastic osmoregulatory physiology. Plasma osmolality, urea, Na(+) and Cl(-) levels increased significantly with increasing environmental salinity. Rectal gland and branchial sodium-potassium ATPase (NKA) activities were unaffected by salinity. Using immunohistochemistry and Western Blotting we found evidence for the presence of the key ion-regulatory proteins vacuolar H(+)-ATPase (VHA), pendrin (Cl(-)/HCO₃(-) co-transporter) and the Na(+)-H(+) exchanger isoform 3 (NHE3) in discrete cells within the branchial epithelia. These results indicate that C. punctatum is a partially euryhaline elasmobranch able to maintain osmo- and ionoregulatory function between environmental salinities of 25‰ and 40‰. As suggested for other elasmobranchs, the gills of C. punctatum likely play a limited role in maintaining Na(+) homeostasis over the salinity range studied, but may play an important role in acid-base balance.
Publisher: The Company of Biologists
Date: 09-2011
DOI: 10.1242/JEB.058156
Abstract: Bull sharks, Carcharhinus leucas, are one of only a few species of elasmobranchs that live in both marine and freshwater environments. Osmoregulation in euryhaline elasmobranchs is achieved through the control and integration of various organs (kidney, rectal gland and liver) in response to changes in environmental salinity. However, little is known regarding the mechanisms of ion transport in the gills of euryhaline elasmobranchs and how they are affected by osmoregulatory challenges. This study was conducted to gain insight into the branchial ion and acid-base regulatory mechanisms of C. leucas by identifying putative ion transporters and determining whether their expression is influenced by environmental salinity. We hypothesised that expression levels of the Na+/K+-ATPase (NKA) pump, Na+/H+ exchanger 3 (NHE3), vacuolar-type H+-ATPase (VHA) and anion exchanger pendrin (PDN) would be upregulated in freshwater (FW) C. leucas. Immunohistochemistry was used to localise all four ion transporters in gills of bull sharks captured in both FW and estuarine/seawater (EST/SW) environments. NHE3 immunoreactivity occurred in the apical region of cells with basolateral NKA expression whereas PDN was apically expressed in cells that also exhibited basolateral VHA immunoreactivity. In accordance with our hypotheses, quantitative real-time PCR showed that the mRNA expression of NHE3 and NKA was significantly upregulated in gills of FW-captured C. leucas relative to EST/SW-captured animals. These data suggest that NHE3 and NKA together may be important in mediating branchial Na+ uptake in freshwater environments, whereas PDN and VHA might contribute to Cl-/HCO3- transport in marine and freshwater bull shark gills.
Publisher: The Company of Biologists
Date: 2018
DOI: 10.1242/JEB.192245
Abstract: Bacterial and viral pathogens can weaken epithelial barriers by targeting and disrupting tight junction (TJ) proteins. Comparatively, however, little is known about the direct effects of fungal pathogens on TJ proteins and their expression. The disease, chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is threatening hibian populations worldwide. Bd is known to infect hibian skin and disrupt cutaneous osmoregulation. However, exactly how this occurs is poorly understood. This study considered the impact of Bd infection on the barrier properties of the Australian green tree frog (Litoria caerulea) epidermis by examining how inoculation of animals with Bd influenced the paracellular movement of FITC-dextran (4 kDa, FD-4) across the skin in association with alterations in the mRNA and protein abundance of select TJ proteins of the epidermal TJ complex. It was observed that Bd infection increased paracellular movement of FD-4 across the skin linearly with fungal infection load. In addition, Bd infection increased transcript abundance of the tricellular TJ (tTJ) protein tricellulin (tric) as well as the bicellular TJ (bTJ) proteins occludin (ocln), claudin (cldn) -1, -4 and the scaffolding TJ protein zonula occludens-1 (zo-1). However, while Tric protein abundance increased in accord with changes in transcript abundance, protein abundance of Cldn-1 was significantly reduced and Ocln protein abundance was unchanged. Data indicate that disruption of cutaneous osmoregulation in L. caerulea following Bd infection occurs, at least in part, by an increase in epidermal paracellular permeability in association with compromised integrity of the epidermal TJ complex.
Publisher: The Company of Biologists
Date: 15-02-2012
DOI: 10.1242/JEB.058032
Abstract: Physiological ecologists have long sought to understand the plasticity of organisms in environments that vary widely among years, seasons and even hours. This is now even more important because human-induced climate change is predicted to affect both the mean and variability of the thermal environment. Although environmental change occurs ubiquitously, relatively few researchers have studied the effects of fluctuating environments on the performance of developing organisms. Even fewer have tried to validate a framework for predicting performance in fluctuating environments. Here, we determined whether reaction norms based on performance at constant temperatures (18, 22, 26, 30 and 34°C) could be used to predict embryonic and larval performance of anurans at fluctuating temperatures (18–28°C and 18–34°C). Based on existing theory, we generated hypotheses about the effects of stress and acclimation on the predictability of performance in variable environments. Our empirical models poorly predicted the performance of striped marsh frogs (Limnodynastes peronii) at fluctuating temperatures, suggesting that extrapolation from studies conducted under artificial thermal conditions would lead to erroneous conclusions. During the majority of ontogenetic stages, growth and development in variable environments proceeded more rapidly than expected, suggesting that acute exposures to extreme temperatures enable greater performance than do chronic exposures. Consistent with theory, we predicted performance more accurately for the less variable thermal environment. Our results underscore the need to measure physiological performance under naturalistic thermal conditions when testing hypotheses about thermal plasticity or when parameterizing models of life-history evolution.
Publisher: Oxford University Press (OUP)
Date: 02-2009
DOI: 10.1093/ICB/ICP002
Publisher: Herpetologists League
Date: 18-06-2019
DOI: 10.1655/D-18-00014
Publisher: Elsevier BV
Date: 06-2018
Publisher: University of Chicago Press
Date: 2014
DOI: 10.1086/671165
Abstract: Many animal populations are in decline as a result of human activity. Conservation practitioners are attempting to prevent further declines and loss of bio ersity as well as to facilitate recovery of endangered species, and they often rely on interdisciplinary approaches to generate conservation solutions. Two recent interfaces in conservation science involve animal behavior (i.e., conservation behavior) and physiology (i.e., conservation physiology). To date, these interfaces have been considered separate entities, but from both pragmatic and biological perspectives, there is merit in better integrating behavior and physiology to address applied conservation problems and to inform resource management. Although there are some institutional, conceptual, methodological, and communication-oriented challenges to integrating behavior and physiology to inform conservation actions, most of these barriers can be overcome. Through outlining several successful ex les that integrate these disciplines, we conclude that physiology and behavior can together generate meaningful data to support animal conservation and management actions. Tangentially, applied conservation and management problems can, in turn, also help advance and reinvigorate the fundamental disciplines of animal physiology and behavior by providing advanced natural experiments that challenge traditional frameworks.
Publisher: Springer Science and Business Media LLC
Date: 24-05-2009
DOI: 10.1007/S00360-009-0368-Y
Abstract: Changes in membrane lipid composition (membrane remodelling) have been associated with metabolic depression in some aestivating snails but has not been studied in aestivating frogs. This study examined the membrane phospholipid composition of two Australian aestivating frog species Cyclorana alboguttata and Cyclorana australis. The results showed no major membrane remodelling of tissue in either frog species, or in mitochondria of C. alboguttata due to aestivation. Mitochondrial membrane remodelling was not investigated in C. australis. Where investigated in C. alboguttata, total protein and phospholipid content, and citrate synthase (CS) and cytochrome c oxidase (CCO) activities in tissues and mitochondria mostly did not change with aestivation in liver. In skeletal muscle, however, CS and CCO activities, mitochondrial and tissue phospholipids, and mitochondrial protein decreased with aestivation. These decreases in muscle indicate that skeletal muscle mitochondrial content may decrease during aestivation. Na(+)K(+)ATPase activity of both frog species showed no effect of aestivation. In C. alboguttata different fat diets had a major effect on both tissue and mitochondrial phospholipid composition indicating an ability to remodel membrane composition that is not utilised in aestivation. Therefore, changes in lipid composition associated with some aestivating snails do not occur during aestivation in these Australian frogs.
Publisher: Springer Science and Business Media LLC
Date: 2015
Publisher: Wiley
Date: 11-2002
Publisher: University of Chicago Press
Date: 05-2019
DOI: 10.1086/702828
Abstract: Diving optimality models predict air breathers to routinely e within aerobic limits, but predator avoidance es may be an exception. Lengthening submergence times during a predation threat may enhance survival probability, and we therefore hypothesized that predator avoidance es in juvenile estuarine crocodiles (Crocodylus porosus) would be partially anaerobically fueled. We also predicted that reliance on anaerobic metabolism would increase at elevated temperatures to offset the faster depletion of body oxygen stores. Crocodiles were maintained at 28° and 34°C for 60 d and subsequently underwent simulated predator avoidance e trials at two test temperatures (28° and 34°C). Blood was s led immediately on surfacing to measure plasma lactate concentrations relative to non ing (control) values. Aerobic e limits (cADL min) were also calculated using known body mass and oxygen storage relationships and rates of ing oxygen consumption and compared with observed e durations. Post e plasma lactate levels were elevated beyond resting levels at both test temperatures, indicating that aerobic thresholds were surpassed during simulated predator avoidance es. Similarly, ≥90% of e durations exceeded cADLs at both test temperatures. Post e plasma lactate concentrations were independent of water temperature and thermal acclimation treatment. Together, these findings suggest that reliance on anaerobiosis during simulated predator avoidance es is important regardless of temperature.
Publisher: The Company of Biologists
Date: 2013
DOI: 10.1242/JEB.087130
Abstract: With the Arctic experiencing one of the most rapid and greatest increases in sea temperatures in modern time, predicting how Arctic marine organisms will respond to elevated temperatures has become critical for conservation biology. Here we examined the thermal sensitivity of cardiorespiratory performance for three closely related species of sculpins that inhabit the Arctic waters, two of which, Gymnocanthus tricuspis and Myoxocephalus scorpioides, have adapted to a restricted range within the Arctic, whereas the third species, Myoxocephalus scorpius, has a wider distribution. We tested the hypothesis that the fish restricted to Arctic cold waters would show reduced cardiorespiratory scope in response to an increase in temperature, as compared with the more eurythermal M. scorpius. As expected from their biogeography, M. scorpioides and G. tricuspis maximised cardiorespiratory performance at temperatures between 1-4oC, whereas M. scorpius maximised performance over a wider range of temperatures (1-10oC). Furthermore, factorial scope for cardiac output collapsed at elevated temperature for the two high-latitude species, negatively impacting their ability to support aerobically driven metabolic processes. Consequently, these results concurred with our hypothesis, suggesting that the sculpin species restricted to the Arctic will likely be negatively impacted by increases in ocean temperatures.
Publisher: Springer Science and Business Media LLC
Date: 14-06-2017
DOI: 10.1038/S41598-017-03605-Z
Abstract: The fungal pathogen Batrachochytrium dendrobatidis ( Bd ) has been implicated in hibian population declines globally. Given that Bd infection is limited to the skin in post-metamorphic hibians, routine skin sloughing may regulate infection. Skin sloughing has been shown to reduce the number of cultivatable microbes on hibian skin, and Bd infection increases skin sloughing rates at high loads. However, it is unclear whether species specific differences in skin sloughing patterns could regulate Bd population growth on the skin, and influence subsequent infection dynamics. We exposed five Australian frog species to Bd , and monitored sloughing rates and infection loads over time. Sloughing reduced Bd load on the ventral skin surface, in all five species, despite wide variation in susceptibility to disease. In the least susceptible species, an increase in sloughing rate occurred at lower infection loads, and sloughing reduced Bd load up to 100%, leading to infection clearance. Conversely, the drop in Bd load with sloughing was only temporary in the more susceptible species. These findings indicate that the ability of sloughing to act as an effective immune defence is species specific, and they have implications for understanding the pattern of Bd population growth on in idual hosts, as well as population-level effects.
Publisher: Wiley
Date: 17-12-2015
DOI: 10.1111/ACV.12186
Publisher: Society for the Study of Amphibians and Reptiles
Date: 06-2013
DOI: 10.1670/12-039
Publisher: University of Chicago Press
Date: 03-2000
DOI: 10.1086/316730
Abstract: The effect of ontogenetic increases in total length on burst swimming performance was investigated in tadpoles of the striped marsh frog (Limnodynastes peronii) over the total-length range of 1. 5-4 cm and Gosner developmental stages 25-38. The burst swimming performance of tadpoles at 10 degrees and 24 degrees C was determined by videotaping startle responses with a high-speed video camera at 200 Hz and analysing the sequences frame by frame. Maximum swimming velocity (Umax) and acceleration (Amax) increased with total length (L) at a rate that was proportionally greater than the increase in total length (i.e., positive allometry exponents >1) and was described by the allometric equations Umax=0.061L1.34 and Amax=1.15L1.11 at 10 degrees C and Umax=0.114L1.34 and Amax=1.54L1. 11 at 24 degrees C. Stride length increased with a total-length exponent of approximately 1 but was unaffected by temperature. Tail-beat frequency was not affected by total length and increased from 7.8+/-0.2 Hz at 10 degrees C to 21.7+/-0.7 Hz at 24 degrees C. Developmental stage did not significantly influence the relationship between total length and Umax or Amax. Furthermore, temperature and the associated changes in water viscosity did not affect the relationship between total length and burst swimming performance. At their Umax, Reynolds numbers ranged from approximately 1,500 in the smaller tadpoles up to 50,000 for the larger animals at 24 degrees C. We suggest the positive allometry of Umax in larval L. peronii was due in part to the increases in tail width (TW) with total length (TW=-1.36L1.66), possibly reflecting the increasing importance of burst swimming performance to survival during larval development.
Publisher: Springer Science and Business Media LLC
Date: 18-03-2017
Publisher: Oxford University Press (OUP)
Date: 26-03-2013
Publisher: Wiley
Date: 11-06-2007
Publisher: The Company of Biologists
Date: 08-03-2022
DOI: 10.1242/JEB.244096
Publisher: The Company of Biologists
Date: 09-2007
DOI: 10.1242/JEB.003137
Abstract: Antarctic fish Pagothenia borchgrevinki in McMurdo Sound,Antarctica, inhabit one of the coldest and most thermally stable of all environments. Sea temperatures under the sea ice in this region remain a fairly constant –1.86°C year round. This study examined the thermal plasticity of cardiac function in P. borchgrevinki to determine whether specialisation to stable low temperatures has led to the loss of the ability to acclimate physiological function. Fish were acclimated to–1°C and 4°C for 4–5 weeks and cardiac output was measured at rest and after exhaustive exercise in fish acutely transferred from their acclimation temperature to –1, 2, 4, 6 and 8°C. In the–1°C acclimated fish, the factorial scope for cardiac output was greatest at –1°C and decreased with increasing temperature. Increases in cardiac output with exercise in the –1°C acclimated fish was achieved by increases in both heart rate and stroke volume. With acclimation to 4°C, resting cardiac output was thermally independent across the test temperatures furthermore, factorial scope for cardiac output was maintained at 4, 6 and 8°C, demonstrating thermal compensation of cardiac function at the higher temperatures. This was at the expense of cardiac function at –1°C, where there was a significant decrease in factorial scope for cardiac output in the 4°C acclimated fish. Increases in cardiac output with exercise in the 4°C acclimated fish at the higher temperatures was achieved by changes in heart rate alone, with stroke volume not varying between rest and exercise. The thermal compensation of cardiac function in P. borchgrevinki at higher temperatures was the result of a change in pumping strategy from a mixed inotropic/chronotropic modulated heart in –1°C acclimated fish at low temperatures to a purely chronotropic modulated heart in the 4°C acclimated fish at higher temperatures. In spite of living in a highly stenothermal cold environment, P. borchgrevinki demonstrated the capacity to thermally acclimate cardiac function to elevated temperatures, thereby allowing the maintenance of factorial scope and the support of aerobic swimming at higher temperatures.
Publisher: Springer Science and Business Media LLC
Date: 24-11-2005
DOI: 10.1007/S00360-004-0460-2
Abstract: This study examined the osmoregulatory status of the euryhaline elasmobranch Carcharhinus leucas acclimated to freshwater (FW) and seawater (SW). Juvenile C. leucas captured in FW (3 mOsm l(-1) kg(-1)) were acclimated to SW (980-1,000 mOsm l(-1) kg(-1)) over 16 days. A FW group was maintained in captivity over a similar time period. In FW, bull sharks were hyper-osmotic regulators, having a plasma osmolarity of 595 mOsm l(-1) kg(-1). In SW, bull sharks had significantly higher plasma osmolarities (940 mOsm l(-1) kg(-1)) than FW-acclimated animals and were slightly hypo-osmotic to the environment. Plasma Na(+), Cl(-), K(+), Mg(2+), Ca(2+), urea and trimethylamine oxide (TMAO) concentrations were all significantly higher in bull sharks acclimated to SW, with urea and TMAO showing the greatest increase. Gill, rectal gland, kidney and intestinal tissue were taken from animals acclimated to FW and SW and analysed for maximal Na(+)/K(+)-ATPase activity. Na(+)/K(+)-ATPase activity in the gills and intestine was less than 1 mmol Pi mg(-1) protein h(-1) and there was no difference in activity between FW- and SW-acclimated animals. In contrast Na(+)/K(+)-ATPase activity in the rectal gland and kidney were significantly higher than gill and intestine and showed significant differences between the FW- and SW-acclimated groups. In FW and SW, rectal gland Na(+)/K(+)-ATPase activity was 5.6+/-0.8 and 9.2+/-0.6 mmol Pi mg(-1) protein h(-1), respectively. Na(+)/K(+)-ATPase activity in the kidney of FW and SW acclimated animals was 8.4+/-1.1 and 3.3+/-1.1 Pi mg(-1) protein h(-1), respectively. Thus juvenile bull sharks have the osmoregulatory plasticity to acclimate to SW their preference for the upper reaches of rivers where salinity is low is therefore likely to be for predator avoidance and/or increased food abundance rather than because of a physiological constraint.
Publisher: Springer Science and Business Media LLC
Date: 10-2021
Publisher: Oxford University Press (OUP)
Date: 2017
Publisher: Elsevier BV
Date: 02-2002
Publisher: Springer Science and Business Media LLC
Date: 1988
DOI: 10.1007/BF00443449
Publisher: The Company of Biologists
Date: 15-04-2010
DOI: 10.1242/JEB.039305
Abstract: Saltwater crocodiles, Crocodylus porosus, possess lingual salt glands which function to remove excess Na+ and Cl− accumulated as a consequence of living in salt water. Little is known about the nature of ion transport systems in C. porosus salt glands and how these systems respond to an osmotic challenge. In the present study, we examined the distribution and regulation of the Na+/K+-ATPase (NKA) pump, specifically the α-(catalytic) subunit in the salt glands of C. porosus chronically acclimated (6 months) to freshwater (FW) or 70% seawater (SW). We hypothesised that in the SW-acclimated C. porosus there would be an up-regulation of the abundance, activity and gene expression of the NKA transporter. NKA was immunolocalised to the lateral and basal membrane of secretory cells. As predicted, the NKA α-subunit was 2-fold more abundant in SW-acclimated C. porosus salt glands. NKA gene expression was also elevated in the salt glands of SW- vs FW-acclimated crocodiles. There was no increase in the specific activity of NKA in SW-acclimated animals and the in vitro rate of oxygen consumption by salt gland slices from SW-acclimated animals was not significantly different from that of FW-acclimated animals. The proportion of tissue oxygen consumption rate attributable to NKA activity was not different between SW- and FW-acclimated animals (approximately 50%). These data suggest that either chronic SW acclimation does not affect NKA in crocodile salt glands in the same manner as seen in other models or crocodiles possess the capacity to moderate NKA activity following prolonged exposure to SW.
Publisher: The Company of Biologists
Date: 2019
DOI: 10.1242/JEB.197392
Publisher: Elsevier BV
Date: 12-2004
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.CBPA.2019.01.004
Abstract: Aquatic organisms, including important cultured species, are forced to contend with acute changes in water temperature as the frequency and intensity of extreme weather events worsen. Acute temperature spikes are likely to threaten aquaculture species, but dietary intervention may play an important protective role. Increasing the concentration of macronutrients, for ex le dietary fat content, may improve the thermal resilience of aquaculture species, however, this remains unexplored. To evaluate this hypothesis, we used two commercially available diets (20% versus 10% crude fat) to examine if dietary fat content improves the growth performance of juvenile barramundi (Lates calcarifer) while increasing their resilience to acute thermal stress. Fish were fed their assigned diets for 28-days before assessing the upper thermal tolerance (CT
Publisher: Wiley
Date: 13-05-2014
DOI: 10.1111/AEC.12150
Publisher: The Royal Society
Date: 26-01-2011
Abstract: Increased ultraviolet-B (UV-B) radiation as a consequence of ozone depletion is one of the many potential drivers of ongoing global hibian declines. Both alone and in combination with other environmental stressors, UV-B is known to have detrimental effects on the early life stages of hibians, but our understanding of the fitness consequences of these effects remains superficial. We examined the independent and interactive effects of UV-B and predatory chemical cues (PCC) on a suite of traits of Limnodynastes peronii embryos and tadpoles, and assessed tadpole survival time in a predator environment to evaluate the potential fitness consequences. Exposure to a 3 to 6 per cent increase in UV-B, which is comparable to changes in terrestrial UV-B associated with ozone depletion, had no effect on any of the traits measured, except survival time in a predator environment, which was reduced by 22 to 28 per cent. Exposure to PCC caused tadpoles to hatch earlier, have reduced hatching success, have improved locomotor performance and survive for longer in a predator environment, but had no effect on tadpole survival, behaviour or morphology. Simultaneous exposure to UV-B and PCC resulted in no interactive effects. These findings demonstrate that increased UV-B has the potential to reduce tadpole fitness, while exposure to PCCs improves their fitness.
Publisher: The Company of Biologists
Date: 15-11-2009
DOI: 10.1242/JEB.033688
Abstract: We investigated the effect of prolonged immobilisation of six and nine months duration on the morphology and antioxidant biochemistry of skeletal muscles in the hibian aestivator Cyclorana alboguttata. We hypothesised that, in the event of atrophy occurring during aestivation,larger jumping muscles were more likely to be preserved over smaller non-jumping muscles. Whole muscle mass (g), muscle cross-sectional area (CSA)(μm2), water content (%) and myofibre number (per mm2) remained unchanged in the cruralis muscle after six to nine months of aestivation however, myofibre area (μm2) was significantly reduced. Whole muscle mass, water content, myofibre number and myofibre CSA remained unchanged in the gastrocnemius muscle after six to nine months of aestivation. However, iliofibularis dry muscle mass, whole muscle CSA and myofibre CSA was significantly reduced during aestivation. Similarly,sartorius dry muscle mass, water content and whole muscle CSA was significantly reduced during aestivation. Endogenous antioxidants were maintained at control levels throughout aestivation in all four muscles. The results suggest changes to muscle morphology during aestivation may occur when lipid reserves have been depleted and protein becomes the primary fuel substrate for preserving basal metabolic processes. Muscle atrophy as a result of this protein catabolism may be correlated with locomotor function, with smaller non-jumping muscles preferentially used as a protein source during fasting over larger jumping muscles. Higher levels of endogenous antioxidants in the jumping muscles may confer a protective advantage against oxidative damage during aestivation however, it is not clear whether they play a role during aestivation or upon resumption of normal metabolic activity.
Publisher: Springer Science and Business Media LLC
Date: 17-07-2007
DOI: 10.1007/S00360-007-0181-4
Abstract: Changes in blood flow are a principal mechanism of thermoregulation in vertebrates. Changes in heart rate will alter blood flow, although multiple demands for limited cardiac output may compromise effective thermoregulation. We tested the hypothesis that regional differences in blood flow during heating and cooling can occur independently from changes in heart rate. We measured heart rate and blood pressure concurrently with blood flow in the crocodile, Crocodylus porosus. We measured changes in blood flow by laser Doppler flowmetry, and by injecting coloured microspheres. All measurements were made under different heat loads, with and without blocking cholinergic and beta-adrenergic receptors (autonomic blockade). Heart rates were significantly faster during heating than cooling in the control animals, but not when autonomic receptors were blocked. There were no significant differences in blood flow distribution between the control and autonomic blockade treatments. In both treatments, blood flow was directed to the dorsal skin and muscle and away from the tail and duodenum during heating. When the heat source was switched off, there was a redistribution of blood from the dorsal surface to the duodenum. Blood flow to the leg skin and muscle, and to the liver did not change significantly with thermal state. Blood pressure was significantly higher during the autonomic blockade than during the control. Thermal time constants of heating and cooling were unaffected by the blockade of autonomic receptors. We concluded that animals partially compensated for a lack of differential heart rates during heating and cooling by redistributing blood within the body, and by increasing blood pressure to increase flow. Hence, measures of heart rate alone are insufficient to assess physiological thermoregulation in reptiles.
Publisher: Elsevier BV
Date: 04-2007
DOI: 10.1016/J.REGPEP.2006.11.011
Abstract: Most avian and reptilian salt glands display marked phenotypic plasticity when animals are exposed to hyperosmotic conditions. In addition, the activity of most salt glands is under considerable control by the nervous system and nerves containing cholinergic, adrenergic and peptidergic neurotransmitters have been identified in avian and reptilian salt gland tissues. The present study sought to determine whether the salt glands of the estuarine crocodile, Crocodylus porosus contain the peptidergic neurotransmitters SP, CGRP, VIP, and PACAP and the gaseous neurotransmitter, NO. In addition, we sought to determine whether there was any evidence for the adaptation of the C. porosus salt gland nervous system to hyperosmotic conditions. Salt glands from freshwater- and saltwater-acclimated C. porosus hatchlings were sectioned and examined immunohistochemically for neurotransmitters within the tissue. Neurons containing SP, CGRP, VIP, PACAP and NO synthase were identified within C. porosus salt glands. There was no difference in the overall number (density) of neurons within SW-acclimated tissues when compared with FW-acclimated animals. However, there was a significant reduction in density of neurons containing SP and PACAP in SW-acclimated animals. C. porosus salt glands display phenotypic plasticity following exposure to hyperosmotic conditions. In addition to cholinergic and adrenergic neurons, they contain a variety of peptidergic neurotransmitters and the gaseous neurotransmitter NO. Additionally, there appears to be some evidence of acclimation of the nervous system of C. porosus to hypersaline conditions, although the functional significance of these changes remains to be determined.
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 12-2003
DOI: 10.1016/S1096-4959(03)00280-X
Abstract: Since the landmark contributions of Homer Smith and co-workers in the 1930s there has been a considerable advance in our knowledge regarding the osmoregulatory strategy of elasmobranch fish. Smith recognised that urea was retained in the body fluids as part of the 'osmoregulatory ballast' of elasmobranch fish so that body fluid osmolality is raised to a level that is iso- or slightly hyper-osmotic to that of the surrounding medium. From studies at that time he also postulated that many marine dwelling elasmobranchs were not capable of adaptation to dilute environments. However, more recent investigations have demonstrated that, at least in some species, this may not be the case. Gradual acclimation of marine dwelling elasmobranchs to varying environmental salinities under laboratory conditions has demonstrated that these fish do have the capacity to acclimate to changes in salinity through independent regulation of Na(+), Cl(-) and urea levels. This suggests that many of the presumed stenohaline marine elasmobranchs could in fact be described as partially euryhaline. The contributions of Thomas Thorson in the 1970s demonstrated the osmoregulatory strategy of a fully euryhaline elasmobranch, the bull shark, Carcharhinus leucas, and more recent investigations have examined the mechanisms behind this strategy in the euryhaline elasmobranch, Dasyatis sabina. Both partially euryhaline and fully euryhaline species utilise the same physiological processes to control urea, Na(+) and Cl(-) levels within the body fluids. The role of the gills, kidney, liver, rectal gland and drinking process is discussed in relation to the endocrine control of urea, Na(+) and Cl(-) levels as elasmobranchs acclimate to different environmental salinities.
Publisher: Wiley
Date: 26-07-2005
Location: United Kingdom of Great Britain and Northern Ireland
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End Date: 12-2017
Amount: $437,000.00
Funder: Australian Research Council
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