Philip Withers

Metabolic and ventilatory physiology of the Barrow Island golden bandicoot (Isoodon auratus barrowensis) and the northern brown bandicoot (Isoodon macrourus)

Publisher: Elsevier BV

Date: 08-2008

DOI: 10.1016/J.JTHERBIO.2008.05.001

Does season or captivity influence the physiology of an endangered marsupial, the numbat (Myrmecobius fasciatus)?

Publisher: Oxford University Press (OUP)

Date: 28-06-2012

DOI: 10.1644/11-MAMM-A-084.2

Thermal, metabolic, hygric and ventilatory physiology of the sandhill dunnart (Sminthopsis psammophila; Marsupialia, Dasyuridae)

Publisher: Elsevier BV

Date: 07-2009

DOI: 10.1016/J.CBPA.2009.03.006

Abstract: We present here the first physiological data for the sandhill dunnart (Sminthopsis psammophila), the second largest (35-44 g) sminthopsine dasyurid marsupial, and report torpor for this species. Their thermoneutral body temperature (34.4 degrees C), thermolability below thermoneutrality (0.062 degrees C degrees C(-1)), and mild hyperthermia above thermoneutrality (35.5 degrees C) are typical of small dunnarts, and dasyurids. Basal metabolic rate (0.80 mL O2 g(-1) h(-1)) is as predicted from mass. Sandhill dunnarts generally conform to the Scholander-Irving model of endothermy, although metabolism increases less than expected and extrapolates to a higher than actual body temperature.Wet (0.22 mL O2 g(-1) h(-1) C(-1)) and dry (2.8 J g(-1) h(-1) degrees C(-1)) thermal conductances were as predicted. Thermoneutral evaporative water loss (1.6 mg g(-1) h(-1)) was only 54% of expected, but this is not significantly different, and more likely reflects variability in the marsupial dataset than an adaptation.Relative water economy resembles that of other small marsupials, rodents and birds, with a point of relative economy of 18 degrees C. Respiratory ventilation closely matches metabolic rate, with minute volume increased at low ambient temperatures by increased breathing rate rather than tidal volume oxygen extraction was constant at about 17%, except during hyperthermia above the thermoneutrality. Torpor conferred significant energetic and hygric benefits. We found no evidence of deviation from allometrically- and phylogenetically-based expectations despite the sandhill dunnart's arid habitat and large (for a dunnart) body mass.

Water balance and arginine vasotocin in the cocooning frog Cyclorana platycephala (Hylidae)

Publisher: University of Chicago Press

Date: 2008

DOI: 10.1086/523856

Abstract: It is well established that forming a cocoon, for frog species capable of doing so, markedly reduces evaporative water loss however, the capacity of cocooned frogs to maintain hydration during extended estivation is not well understood. The combined effects of long-term estivation and water loss were examined in the cocoon-forming species Cyclorana platycephala by assessing the hydration state of the frogs throughout a 15-mo estivation period. Frogs lost mass throughout the 15-mo period to a maximum of 36%+/-6.5% of their initial standard mass. Plasma osmolality reached maximal levels by the ninth month of estivation at 487 mOsm kg(-1) and then remained stable to the fifteenth month of estivation. Urine osmolality continued to increase to the fifteenth month of estivation, at which point plasma and urine concentrations were isosmotic. The use of bladder water to counter losses from circulation was indicated by the relatively slow rate of increase in plasma osmolality with mass loss and the progressive increase in urine osmolality. For estivating frogs, evidence was found for a possible threshold relationship between plasma osmolality and plasma arginine vasotocin (AVT) concentration. After estivation, plasma AVT concentrations decreased markedly after 15-mo estivators were placed in water for 2 h, suggesting that high levels of AVT may not be integral to rapid rehydration in this species.

Effects of long-term captivity on thermoregulation, metabolism and ventilation of the southern brown bandicoot (Marsupialia: Peramelidae)

Publisher: Springer Science and Business Media LLC

Date: 27-10-2006

DOI: 10.1007/S00360-006-0124-5

Abstract: Thermoneutral metabolic and ventilatory parameters were measured every 3 months over 2 years for southern brown bandicoots held in captivity, and from a nearby reserve. Captive bandicoots were 130 g (9.9%) heavier than wild bandicoots. Long-term captivity had no effect on body temperature, basal metabolic rate (oxygen consumption), thermal conductance or respiratory ventilation, but there was an effect on carbon dioxide production, respiratory exchange ratio and total evaporative water loss (values were between 15 and 25% higher for captive than for wild bandicoots). Diet may be influencing these aspects of captive bandicoot physiology the diet of captive bandicoots would be considerably different to that of wild bandicoots. Water availability seems to have a minimal effect. This study has important implications regarding physiological measurement for captive and wild mammals. For bandicoots at least, captive animals are equivalent to wild animals for some physiological parameters at thermoneutrality (body temperature, resting metabolic rate and thermal conductance), but not others.

Effects of Measurement Duration on the Determination of Basal Metabolic Rate and Evaporative Water Loss of Small Marsupials: How Long Is Long Enough?

Publisher: University of Chicago Press

Date: 09-2009

DOI: 10.1086/603654

Abstract: We examined the time course for measurement of basal metabolic rate (BMR measured as O(2) consumption and CO(2) production) and standard evaporative water loss (EWL) for six species of small marsupial to determine the minimum time required to achieve basal/standard values. There was a highly significant effect of measurement duration on measured physiological variables with values for O(2) consumption, CO(2) production, and EWL decreasing with time for all species. The time required to attain values statistically indistinguishable from minimal differed significantly between species, but in general O(2) consumption rate reached basal values after 4.3 h, CO(2) production after 4.5 h, and evaporative water loss after 5.2 h. For 16 BMR measurements of small marsupial species in the literature, with experimental duration provided, 10 were for less than 4 h, suggesting that their BMR values might be overestimates. For EWL, three of the four published values for small marsupials may be overestimates. It is clear that appropriate experimental duration is an important component of the measurement protocol for both BMR and standardized water loss, which needs to be rigorously observed in future studies.

Ecological consequences of temperature regulation: Why might the mountain pygmy possumBurramys parvusneed to hibernate near underground streams?

Publisher: Informa UK Limited

Date: 22-05-2014

DOI: 10.4161/TEMP.29292

Allometry of evaporative water loss in marsupials: implications of the effect of ambient relative humidity on the physiology of brushtail possums(Trichosurus vulpecula)

Publisher: The Company of Biologists

Date: 09-2008

DOI: 10.1242/JEB.019463

Abstract: To better understand the effects of ambient relative humidity (RH) on physiological variables and the implications of RH-correcting evaporative water loss (EWL) data for marsupials, we examined the effect of RH on EWL,body temperature (Tb), metabolic rate (MR) and thermal conductance (C) of the brushtail possum (Trichosurus vulpecula), a medium-sized marsupial. Correcting EWL data for 27 species of marsupial for water vapour pressure deficit (ΔWVP) in the chamber during measurement significantly increased, rather than decreased, the variability of the allometric relationship for EWL. For the brushtail possum,both ambient temperature (Ta) and RH significantly affected EWL. At Ta=25°C, EWL was independent of RH at≤63% RH, but decreased linearly at higher RH values. At Ta=30°C, EWL was significantly related to RH from 26%to 92% RH. There was a significant effect of Ta on Tb and dry thermal conductance (Cdry higher at 30°C), but no effect of RH. For MR and wet thermal conductance(Cwet) there was a significant effect of Ta (MR higher and Cwet lower at 25°C), and RH at Ta=30°C (MR higher and Cwet lower at the lowest RH) but not at 25°C. Our results indicate that brushtail possums do not necessarily show the linear relationship between ambient RH and EWL expected for an endotherm, possibly because of behavioural modification of their immediate microclimate. This may account for the failure of WVP deficit correction to improve the allometric EWL relationship for marsupials. Chamber RH is an important environmental factor to be considered when measuring standard physiological variables such as MR and Cwet.

Reexamining Echidna Physiology: The Big Picture forTachyglossus aculeatus acanthion

Publisher: University of Chicago Press

Date: 05-2016

DOI: 10.1086/686716

Abstract: The early ergence of monotremes and therian mammals has resulted in considerable interest in the comparative physiology of the short-beaked echidna (Tachyglossus aculeatus), the most common and widespread living monotreme. However, there are many and varied interpretations of its physiology, reflecting the many and varied studies, limitations and uncertainties of aspects of some previous studies, and potential differences between the various subspecies. Consequently, we thoroughly examine here the standardized physiology of the most widely distributed subspecies of short-beaked echidna (T. aculeatus acanthion) over a wide range of ambient temperatures to definitively assess its physiology in a comparative context. We conclude that the low and variable body temperature of the short-beaked echidna is physiologically "primitive," but it also reflects adaptation to its myrmecophagous niche. Other aspects of its physiology are more typically mammalian. A low metabolic rate reflects its low body temperature, and ventilatory variables are matched to accommodate a modest gas exchange requirement. Thermal conductance is typical for a mammal of equivalent mass. In contrast to previous studies, we demonstrate that short-beaked echidnas can enhance evaporative water loss above thermoneutrality, like other mammals, with a similar capacity for evaporative heat loss. Cooling of their nasal blood sinus with nasal mucous may contribute to this enhanced evaporative cooling. Their capacity to evaporatively cool explains how their distribution can include habitats where ambient temperature, even in shelters, exceeds their supposed critical thermal limit.

Water and energy balance of the thorny devil Moloch horridus: is the devil a sloth?

Publisher: Brill

Date: 1995

DOI: 10.1163/156853895X00181

Abstract: Rates of turnover of water, energy and sodium were measured for free-ranging thorny devils (Moloch horridus), which are myrmecophagous agamid lizards, in a semi-arid Western Australian habitat. There were significant differences in body water content and water turnover rate (WTR) measurements for cool, wet, average and hot periods, although the field metabolic rate (FMR) and sodium turnover (NaTR) rate did not differ significantly between weather conditions. The thorny devil had a substantially lower field WTR during dry periods (10-15 ml kg-1 d-1) than expected for semi-arid and arid lizards, although the WTR was higher in wet conditions (30-35 ml kg-1 d-1). The field metabolic rate of thorny devils (0.134 ml CO2 g-1 h-1) was only slightly less than that expected for a semi-arid/lizard (0.178 ml CO2 g-1 h-1), despite the apparently slothful nature of the thorny devil. The sodium turnover rate of the thorny devil (1.5-2.5 mmol kg-1 d-1) was within the range reported for other semi-arid/arid lizards. The field metabolic rate of the thorny devils suggests that they consume about 750 ants per day. The ratio of water to energy turnover measured for thorny devils in the field (0.11 ml H2O kj-1) was the same as that predicted from the composition of ants and their digestibility by thorny devils (0.11 ml H2O kj-1). However, the ratios of sodium-to-energy turnover (30 μmol Na+ kj-1) and sodium-to-water turnover (277 μmol ml H2O-1) were substantially higher than expected ratios (10 and 89 respectively).

Evaporative water loss, relative water economy and evaporative partitioning of a heterothermic marsupial, the monito del monte (Dromiciops gliroides)

Publisher: The Company of Biologists

Date: 15-08-2012

DOI: 10.1242/JEB.070433

Abstract: We examine here evaporative water loss, economy and partitioning at ambient temperatures from 14 to 33°C for the monito del monte (Dromiciops gliroides), a microbiotheriid marsupial found only in temperate rainforests of Chile. The monito's standard evaporative water loss (2.58 mg g−1 h−1 at 30°C) was typical for a marsupial of its body mass and phylogenetic position. Evaporative water loss was independent of air temperature below thermoneutrality, but enhanced evaporative water loss and hyperthermia were the primary thermal responses above the thermoneutral zone. Non-invasive partitioning of total evaporative water loss indicated that respiratory loss accounted for 59–77% of the total, with no change in respiratory loss with ambient temperature, but a small change in cutaneous loss below thermoneutrality and an increase in cutaneous loss in and above thermoneutrality. Relative water economy (metabolic water production/evaporative water loss) increased at low ambient temperatures, with a point of relative water economy of 15.4°C. Thermolability had little effect on relative water economy, but conferred substantial energy savings at low ambient temperatures. Torpor reduced total evaporative water loss to as little as 21% of normothermic values, but relative water economy during torpor was poor even at low ambient temperatures because of the relatively greater reduction in metabolic water production than in evaporative water loss. The poor water economy of the monito during torpor suggests that negative water balance may explain why hibernators periodically arouse to normothermia, to obtain water by drinking or via an improved water economy.

Numbats and aardwolves—how low is low? A re-affirmation of the need for statistical rigour in evaluating regression predictions

Publisher: Springer Science and Business Media LLC

Date: 26-04-2006

DOI: 10.1007/S00360-006-0085-8

Abstract: Many comparative physiological studies aim to determine if a particular species differs from a prediction based on a linear allometric regression for other species. However, the judgment as to whether the species in question conforms to this allometric relationship is often not based on any formal statistical analysis. An appropriate statistical method is to compare the new species' value with the 95% confidence limits for predicting an additional datum from the relationship for the other species. We examine the basal metabolic rate (BMR) of the termitivorous numbat (Myrmecobius fasciatus) and aardwolf (Proteles cristatus) to demonstrate the use of the 95% prediction limits to determine statistically if they have a lower-than-expected BMR compared to related species. The numbat's BMR was 83.6% of expected from mass, but fell inside the 95% prediction limits for a further datum a BMR < 72.5% of predicted was required to fall below the one-tail 95% prediction limits. The aardwolf had a BMR that was only 74.2% of predicted from the allometric equation, but it also fell well within the 95% prediction limits a BMR of only 41.8% of predicted was necessary to fall below the one-tail 95% prediction limits. We conclude that a formal statistical approach is essential, although it is difficult to demonstrate that a single species statistically differs from a regression relationship for other species.

Physiological responses of a rodent to heliox reveal constancy of evaporative water loss under perturbing environmental conditions

Publisher: American Physiological Society

Date: 15-10-2014

DOI: 10.1152/AJPREGU.00051.2014

Abstract: Total evaporative water loss of endotherms is assumed to be determined essentially by biophysics, at least at temperatures below thermoneutrality, with evaporative water loss determined by the water vapor deficit between the animal and the ambient air. We present here evidence, based on the first measurements of evaporative water loss for a small mammal in heliox, that mammals may have a previously unappreciated ability to maintain acute constancy of total evaporative water loss under perturbing environmental conditions. Thermoregulatory responses of ash-grey mice ( Pseudomys albocinereus) to heliox were as expected, with changes in metabolic rate, conductance, and respiratory ventilation consistent with maintaining constancy of body temperature under conditions of enhanced heat loss. However, evaporative water loss did not increase in heliox. This is despite our confirmation of the physical effect that heliox augments evaporation from nonliving surfaces, which should increase cutaneous water loss, and increases minute volume of live ash-grey mice in heliox to accommodate their elevated metabolic rate, which should increase respiratory water loss. Therefore, mice had not only a thermoregulatory but also a hygroregulatory response to heliox. We interpret these results as evidence that ash-grey mice can acutely control their evaporative water loss under perturbing environmental conditions and suggest that hygroregulation at and below thermoneutrality is an important aspect of the physiology of at least some small mammals.

Ventilatory physiology of the numbat ( Myrmecobius fasciatus )

Publisher: Springer Science and Business Media LLC

Date: 03-2004

DOI: 10.1007/S00360-003-0394-0

Abstract: This study examines the ventilatory physiology of the numbat (Myrmecobius fasciatus), a small to medium-sized (550 g) termitivorous marsupial. Ventilatory parameters at thermoneutrality reflect the slightly low (83% of predicted) basal metabolic rate of the numbat, with ventilation frequency (fR 30.6+/-3.65 breaths min(-1)), tidal volume [VT 6.0+/-0.66 ml at body temperature and pressure, saturated (BTPS)] and consequently minute volume (VI 117.7+/-15.22 ml min(-1) BTPS) all being 80-87% of that expected for a marsupial of similar body mass. Oxygen extraction was 27.7+/-1.37% in the thermoneutral zone. As is typical of marsupials, numbats accommodated increased oxygen consumption rates at ambient temperatures (Ta) below the thermoneutral zone by increasing minute volume (up to 411.2+/-43.98 ml min(-1) BTPS at Ta=10 degrees C) rather than oxygen extraction. Minute volume at 10 degrees C increased more by changes in ventilation frequency (up to 45.5+/-4.85 breaths min(-1)) than tidal volume (9.4+/-1.03 ml, BTPS), as is also typical for a small-medium sized marsupial.

Marsupials don't adjust their thermal energetics for life in an alpine environment

Publisher: Informa UK Limited

Date: 30-03-2016

DOI: 10.1080/23328940.2016.1171280

Metabolic physiology of the numbat ( Myrmecobius fasciatus )

Publisher: Springer Science and Business Media LLC

Date: 12-2002

DOI: 10.1007/S00360-002-0294-8

Abstract: The numbat (Myrmecobius fasciatus) is unique amongst marsupials as it is exclusively diurnal, feeds only on termites and is semi-fossorial. This study examines the thermal and metabolic physiology of the numbat to determine if its physiology reflects its phylogeny, diet and semi-fossorial habit. Numbats (mean adult body mass 552 g) were able to regulate body temperature at ambient temperatures of 15-30 degrees C, with a body temperature at thermoneutrality (30 degrees C) of 34.1 degrees C. The thermoneutral body temperature was not significantly different from that predicted for an equivalent-sized marsupial. Basal metabolic rate, measured at 30 degrees C, was 0.389 +/- 0.025 ml O(2) g(-1) h(-1), and was slightly but not significantly lower at 82.5% of that predicted for a typical marsupial of equivalent body mass. Metabolic rate increased with decreasing ambient temperatures below 30 degrees C. Patterns of metabolic cycling observed for completely inactive numbats at ambient temperatures below 30 degrees C are likely to be related to sleep phase. Wet thermal conductance of 1.94 J g(-1) h(-1) degrees C(-1) (at 30 degrees C) was 131% of that predicted for a marsupial. Evaporative water loss of the numbat remained constant below the thermoneutral zone (<30 degrees C) at approximately 0.6 ml g(-1) h(-1), only 47.4% of that predicted for a marsupial. It increased to 1.01 +/- 0.16 ml g(-1) h(-1) at an ambient temperature of 32.5 degrees C. The thermal and metabolic physiology of the numbat is generally similar to that expected for other marsupials, and is also comparable to that of termitivorous placental mammals. Thus the reduction in body temperature and basal metabolic rate of placental termitivores is a "marsupial-like" low energy turnover physiology, and the numbat being a marsupial already has an appropriate physiology to survive exclusively on a low energy diet of termites.

Thermoregulatory role of insensible evaporative water loss constancy in a heterothermic marsupial

Publisher: The Royal Society

Date: 11-2017

DOI: 10.1098/RSBL.2017.0537

Abstract: ‘Insensible’ evaporative water loss of mammals has been traditionally viewed as a passive process, but recent studies suggest that insensible water loss is under regulatory control, although the physiological role of this control is unclear. We test the hypothesis that regulation of insensible water loss has a thermoregulatory function by quantifying for the first time evaporative water loss control, along with metabolic rate and body temperature, of a heterothermic mammal during normothermia and torpor. Evaporative water loss was independent of ambient relative humidity at ambient temperatures of 20 and 30°C, but not at 25°C or during torpor at 20°C. Evaporative water loss per water vapour pressure deficit had a positive linear relationship with relative humidity at ambient temperatures of 20 and 30°C, but not at 25°C or during torpor at 20 or 25°C. These findings suggest that insensible water loss deviates from a physical model only during thermoregulation, providing support for the hypothesis that regulation of insensible evaporative water loss has a thermoregulatory role.

Biogeographical effects on body mass of native Australian and introduced mice, Pseudomys hermannsburgensis and Mus domesticus: an inquiry into Bergmann's Rule

Publisher: CSIRO Publishing

Date: 2008

DOI: 10.1071/ZO08086

Abstract: We investigated interactions of body mass with geographical location, and five climatic measures for two Australian rodents, the native Australian sandy inland mouse (Pseudomys hermannsburgensis) and the introduced house mouse (Mus domesticus). Correlation and regression analyses identified interactions of body mass with latitude, longitude, average highest maximum and lowest minimum temperatures, average annual rainfall, rainfall variability, and aridity. There was a significant correlation of body mass with latitude and longitude for Mus domesticus and P. hermannsburgensis. House mice were heavier in the south and east, and sandy inland mice were heavier in the north and east. M. domesticus conforms to Bergmann’s Rule, while P. hermannsburgensis does not. Maximum temperature, aridity and rainfall variability significantly influenced body mass of M. domesticus, which was heavier at cooler maxima, in less arid areas, and in areas of greater rainfall variability. Only aridity significantly influenced body mass of P. hermannsburgensis, which was heavier in more arid areas. Temperature did not interact significantly with body mass. After accounting for climatic variables, there was still a significant relationship between the residuals of body mass with locality for both species, with a negative influence of latitude and a positive influence of longitude in both the latitudinal interaction for both species was converse to Bergmann’s Rule. We suggest that latitude, ambient temperature and other selection pressures (such as aridity or productivity) can act in opposing directions, and speculate that the influence of other factors, such as food availability or sociality, may be more important than latitude or ambient temperature.

Effects of experiment start time and duration on measurement of standard physiological variables

Publisher: Springer Science and Business Media LLC

Date: 23-01-2011

DOI: 10.1007/S00360-011-0551-9

Abstract: Duration and start time of respirometry experiments have significant effects on the measurement of basal values for several commonly measured physiological variables (metabolic rate, evaporative water loss and body temperature). A longer measurement duration reduced values for all variables for all start times, and this was an effect of reduced animal activity rather than random s ling. However, there was also an effect of circadian rhythm on the timing of minimal physiological values. Experiment start time had a significant effect on time taken to reach minimal values for all variables, ranging from 0400 hours ± 38 min (body temperature, start time 2300 hours) to 0854 hours ± 52 min (evaporative water loss, start time 1700 hours). It also influenced the time of day that minimal values were obtained, ranging from 2224 hours ± 40 min (carbon dioxide production, start time 1500 hours) to 0600 hours ± 57 min (oxygen consumption, start time 2300 hours), and the minimum values measured. Consequently, both the measurement duration and the experiment start time should be considered in experimental design to account for both a handling and a circadian effect on the animal's physiology. We suggest that experiments to measure standard physiological variables for small diurnal birds should commence between 1700 and 2100 hours, and measurement duration should be at least 9 h.

The private life of echidnas: using accelerometry and GPS to examine field biomechanics and assess the ecological impact of a widespread, semi-fossorial monotreme

Publisher: The Company of Biologists

Date: 15-10-2016

DOI: 10.1242/JEB.143867

Abstract: The short-beaked echidna (Tachyglossus aculeatus) is a monotreme and therefore provides a unique combination of phylogenetic history, morphological differentiation and ecological specialisation for a mammal. The echidna has a unique appendicular skeleton, a highly specialised myrmecophagous lifestyle and a mode of locomotion that is neither typically mammalian nor reptilian, but has aspects of both lineages. We therefore were interested in the interactions of locomotor biomechanics, ecology and movements for wild, free-living short-beaked echidnas. To assess locomotion in its complex natural environment, we attached both GPS and accelerometer loggers to the back of echidnas in both spring and summer. We found that the locomotor biomechanics of echidnas is unique, with lower stride length and stride frequency than reported for similar-sized mammals. Speed modulation is primarily accomplished through changes in stride frequency, with a mean of 1.39 Hz and a maximum of 2.31 Hz. Daily activity period was linked to ambient air temperature, which restricted daytime activity during the hotter summer months. Echidnas had longer activity periods and longer digging bouts in spring compared with summer. In summer, echidnas had higher walking speeds than in spring, perhaps because of the shorter time suitable for activity. Echidnas spent, on average, 12% of their time digging, which indicates their potential to excavate up to 204 m3 of soil a year. This information highlights the important contribution towards ecosystem health, via bioturbation, of this widespread Australian monotreme.

Comparative thermoregulatory physiology of two dunnarts, Sminthopsis macroura and Sminthopsis ooldea (Marsupialia : Dasyuridae)

Publisher: CSIRO Publishing

Date: 2012

DOI: 10.1071/ZO12034

Abstract: Metabolic rate and evaporative water loss (EWL) were measured to quantify the thermoregulatory patterns of two dasyurids, the stripe-faced dunnart (Sminthopsis macroura) and the Ooldea dunnart (S. ooldea) during acute exposure to Ta between 10 and 35°C. S. macroura maintained consistent Tb across the Ta range, whereas S. ooldea was more thermolabile. The metabolic rate of both species decreased from Ta = 10°C to BMR at Ta = 30°C. Mass-adjusted BMR at Ta = 30°C was the same for the two species, but there was no common regression of metabolic rate below the thermoneutral zone (TNZ). There was no significant difference between the species in allometrically corrected EWL at Ta = 30°C. Total EWL increased significantly at Ta = 10 and 35°C compared with the TNZ for S. macroura, but was consistent across the Ta range for S. ooldea. At any Ta below the TNZ, S. macroura required more energy per gram of body mass than S. ooldea, and had a higher EWL at the lower critical Ta. By being thermolabile S. ooldea reduced its energetic requirements and water loss at low Ta. The more constant thermoregulatory strategy of S. macroura may allow it to exploit a broad climatic envelope, albeit at the cost of higher energetic and water requirements. Since S. ooldea does not expend as much energy and water on thermoregulation this may be a response to the very low productivity, ‘hyperarid’ conditions of its central Australian distribution.

Water costs of gas exchange by a speckled cockroach and a darkling beetle

Publisher: MDPI AG

Date: 14-09-2020

DOI: 10.3390/INSECTS11090632

Abstract: Respiratory water loss during metabolic gas exchange is an unavoidable cost of living for terrestrial insects. It has been suggested to depend on several factors, such as the mode of gas exchange (convective vs. diffusive), species habitat (aridity), body size and measurement conditions (temperature). We measured this cost in terms of respiratory water loss relative to metabolic rate (respiratory water cost of gas exchange RWL/V˙CO2) for adults of two insect species, the speckled cockroach (Nauphoeta cinerea) and the darkling beetle (Zophobas morio), which are similar in their mode of gas exchange (dominantly convective), habitat (mesic), body size and measurement conditions, by measuring gas exchange patterns using flow-through respirometry. The speckled cockroaches showed both continuous and discontinuous gas exchange patterns, which had significantly a different metabolic rate and respiratory water loss but the same respiratory water cost of gas exchange. The darkling beetles showed continuous gas exchange pattern only, and their metabolic rate, respiratory water loss and respiratory cost of gas exchange were equivalent to those cockroaches using continuous gas exchange. This outcome from our study highlights that the respiratory water cost of gas exchange is similar between species, regardless of gas exchange pattern used, when the confounding factors affecting this cost are controlled. However, the total evaporative water cost of gas exchange is much higher than the respiratory cost because cuticular water loss contributes considerably more to the overall evaporative water loss than respiratory water. We suggest that the total water cost of gas exchange is likely to be a more useful index of environmental adaptation (e.g., aridity) than just the respiratory water cost.

Avian torpor or alternative thermoregulatory strategies for overwintering?

Publisher: The Company of Biologists

Date: 04-2017

DOI: 10.1242/JEB.154633

Abstract: It is unclear whether torpor really is uncommon amongst passerine birds. We therefore examined body temperature and thermoregulatory strategies of an Austral passerine, the white-browed babbler (Pomatostomus superciliosus), which has characteristics related to a high probability of torpor use it is a sedentary, insectivorous, cooperative breeding species, which we studied during winter in a temperate habitat. Wild, free-living babblers maintained normothermy overnight, even at sub-zero ambient temperatures, with a mean minimum body temperature of 38.5±0.04°C that was independent of minimum black bulb temperature. Physiological variables measured in the laboratory revealed that babblers had a low basal metabolic rate and evaporative water loss, but their body temperature and thermal conductance were typical of those of other birds and they had a typical endothermic response to low ambient temperature. Huddling yielded significant energy savings at low temperatures and a roost nest created a microclimate that buffered against low temperatures. Low basal energy requirements, communal roosting and the insulation of a roost nest confer sufficient energetic benefits, allowing babblers to meet energy requirements without resorting to heterothermia, even in their depauperate, low-productivity landscape, suggesting that passerine birds use alternatives to torpor to balance their energy budgets when possible.

Field metabolism and turnover in the golden bandicoot (isoodon auratus) and other small mammals from Barrow Island, Western Australia

Publisher: CSIRO Publishing

Date: 1994

DOI: 10.1071/ZO9940029

Abstract: Barrow Island, which lies about 90 km north of Onslow off the arid Western Australian Pilbara coast, experienced its driest year on record in 1990 with a total of only 122.4 mm of rain. Golden bandicoots captured in November 1990 evidenced poor condition and mean body mass was a low 242.6 +/- 10.9 g with-a total body water content (TBW) of 76.3 +/- 1.4%. Despite this substantial loss of body water and solids, the animals maintained water and electrolyte balance during the period of turnover [water influx 79.5 +/- 6.9 v. efflux 83.3 +/- 5-7 mL (kg0.82 day)-1 and sodium influx 4.9 +/- 0.7 v. efflux 5.3 +/- 0.7 mmol (kg day)-1]. By April 1991, although only a further 37.4 mm of rain had been recorded on Barrow Island, the condition of the bandicoots had improved markedly, as a result of exploitation of insect resources, and their mean body mass had increased to 306.5 +/- 22.6 g and TBW decreased to 62.5 +/- 1.4% (both P 0.001), the latter reflecting enhanced fat stores. This general improvement in condition of the bandicoots was in marked contrast to that of other herbivorous marsupials on the island. Rates of water and sodium turnover of the golden bandicoots were, however, not significantly different from those measured in the previous November, Field Metabolic Rates (FMRs), measured with doubly labelled water ((HHO))-H-3-O-18, were extremely low, averaging only 0.45 +/- 0.26 mL CO2 (g h)-1, which is very close to laboratory estimates of 0.35 +/- 0.09 mL O2(g h)-1 for the basal metabolic rate of this species. A major cyclone struck Barrow Island on 3 March 1992, with 162 mm of rain falling in 24 h, and turnover measurements in May of that year revealed a substantial increase in rates of water flux. Mean body mass further increased to 332.6 +/- 8.5 g and TBW averaged 61.8 +/- 1.1%. Water turnover rates were significantly elevated when compared with April of the previous year with an influx of 112.5 +/- 7.3 and an efflux of 119.0 +/- 7.6 mL (kg0.82 day)-1 respectively (both P = 0.001). Rates of sodium turnover, however, were only slightly lower at 3.6 +/- 0.5 and 4.1 +/- 0.5 mmol (kg day)-1 for influx and efflux respectively (P = 0.056 for influx only), suggesting a slight decrease in the average sodium content of the diet. The volume of water required to maintain hygric balance was estimated by regression analysis at 26.7 mL day-1 [=88.3 mL (kg0.82 day)-1] in November 1990, and 33-9 mL day-1 [=85.2 mL (kg0.82 day)-1] in May 1992, following rain. The FMR of eight bandicoots was very significantly elevated to 1.39 +/- 0.23 mL CO2 (g h)-1 after rain, which is substantially higher than even the FMR of 0.91 +/- 0.07 mL CO2(g h)-1, or 644 kJ day-1, reported for the closely related southern brown bandicoot (Isoodon obesulus) studied in the region of Perth by Nagy et al. (1991). Turnover rates of water and sodium for two rodent species, the Barrow Island mouse (Pseudomys nanus) and the rock rat (Zyzomys argurus), were very similar to those recorded for golden bandicoots in the dry period, but FMRs were a little higher at 0.80 +/- 0.26 and 0.59 +/- 0-36 mL CO2(g h)-l respectively. The FMR of Barrow Island mice increased very significantly to a mean of 2.73 +/- 0.50 mL CO2(g h)-l after rain, but rock rats were not caught at this time. The data document the impressive ability of these mammals to avail themselves of extremely limited resources and maintain physiological homoiostasis under conditions of extreme aridity.

Can birds do it too? Evidence for convergence in evaporative water loss regulation for birds and mammals

Publisher: The Royal Society

Date: 15-11-2017

DOI: 10.1098/RSPB.2017.1478

Abstract: Birds have many physiological characteristics that are convergent with mammals. In the light of recent evidence that mammals can maintain a constant insensible evaporative water loss (EWL) over a range of perturbing environmental conditions, we hypothesized that birds might also regulate insensible EWL, reflecting this convergence. We found that budgerigars ( Melopsittacus undulatus ) maintain EWL constant over a range of relative humidities at three ambient temperatures. EWL, expressed as a function of water vapour pressure deficit, differed from a physical model where the water vapour pressure deficit between the animal and the ambient air is the driver of evaporation, indicating physiological control of EWL. Regulating EWL avoids thermoregulatory impacts of varied evaporative heat loss changes in relative humidity had no effect on body temperature, metabolic rate or thermal conductance. Our findings that a small bird can regulate EWL are evidence that this is a common feature of convergently endothermic birds and mammals, and may therefore be a fundamental characteristic of endothermy.

Small Alpine Marsupials Regulate Evaporative Water Loss, Suggesting a Thermoregulatory Role Rather than a Water Conservation Role

Publisher: University of Chicago Press

Date: 05-2022

DOI: 10.1086/719735

Abstract: AbstractWe show here that evaporative water loss (EWL) is constant over a wide range of ambient relative humidity for two species of small, mesic habitat dasyurid marsupials (

Environmental physiology of a small marsupial inhabiting arid floodplains

Publisher: Elsevier BV

Date: 09-2010

DOI: 10.1016/J.CBPA.2010.04.018

Abstract: Giles' planigale (Planigale gilesi) is among the smallest extant marsupials and inhabits deep soil cracks in arid floodplains. We examined whether its physiology shows specific adaptations to its extreme habitat. Metabolic rate, body temperature, evaporative water loss and thermal conductance were measured for eight planigales (average mass 9 g) exposed to four different ambient temperatures ranging from 10 degrees C to 32 degrees C. Water economy and respiratory variables were measured for the first time in this species. All of these standard physiological variables conformed to allometrically-predicted values for a marsupial. All variables were significantly affected by ambient temperature, except tidal volume and dry thermal conductance. Metabolic rate increased substantially at low ambient temperatures, as required to maintain a relatively constant body temperature of about 32-34 degrees C. This increased oxygen demand was accommodated by increased ventilation rather than increased oxygen extraction. Planigales had a comparatively high point of relative water economy of 19.1 degrees C, consistent with their small body size and arid habitat. Torpor reduced energy expenditure by 79% and evaporative water loss by 62%. Our study suggests that torpor use, along with behavioural adaptations, suffice for P. gilesi to live underground in arid habitats without further physiological adaptations.

Thermal, Metabolic, and Hygric Physiology of the Little Red Kaluta,Dasykaluta rosamondae(Dasyuromorphia: Dasyuridae)

Publisher: Oxford University Press (OUP)

Date: 02-06-2009

DOI: 10.1644/08-MAMM-A-286R.1

Two independent approaches to assessing the constancy of evaporative water loss for birds under varying evaporative conditions

Publisher: Elsevier BV

Date: 11-2021

DOI: 10.1016/J.CBPA.2021.111041

Abstract: We examine here the effects on evaporative water loss, at and below thermoneutrality, of perturbing the evaporative environment for the red-capped parrot (Purpureicephalus spurius) by modifying the ambient relative humidity or the diffusive properties of the ambient environment using a helium‑oxygen mix (helox). We found that evaporative water loss did not change with relative humidity at an ambient temperature of 30 °C, but there was a negative relationship for evaporative water loss with relative humidity at 20 and 25 °C. The evaporative water loss per water vapour pressure deficit between the bird and its ambient environment was not constant with relative humidity, as would be expected for a physical effect (slope = 0) rather there was a significant positive relationship with relative humidity at ambient temperatures of 25 and 30 °C. Consequently, we conclude that the red-capped parrot can physiologically control its EWL over a range of relative humidities. For the first time for a bird species, we also confirmed EWL control using a second methodology to perturb the evaporative environment, and demonstrated that a more diffusive helox atmosphere has no effect on evaporative water loss of live birds, but evaporative water loss was higher for dead birds in helox compared to air. Our results for evaporative water loss and other physiological variables for red-capped parrots are consistent with the hypothesis that evaporative water loss is under physiological control.

Metabolism and water flux of captive and free-living Australian parrots

Publisher: CSIRO Publishing

Date: 1991

DOI: 10.1071/ZO9910131

Abstract: Occupation of desert environments often requires evolutionary specialisations that minimise food and water requirements. One physiological adjustment to living in a hot, dry climate that has been found in several laboratory studies of birds is a reduced basal metabolic rate (BMR), which often translates into a diminished rate of evaporative water loss (EWL). In free-living birds, these physiological traits are thought to result in a lower field metabolic rate and water flux. We studied metabolism and water flux of a number of species of Australian parrots, both in the laboratory and in the field. After combining our laboratory data with values from the literature, we performed allometric analyses to search for evolutionary specialisation in metabolism and water flux in desert-adapted parrots. Our data do not support the idea that parrots living in arid environments have a reduced BMR. Field metabolic rates of parrots from western Australia were indistinguishable from those of other nonpasserine birds. Laboratory EWL was significantly lower for parrots living in desert environments than for those occupying more mesic habitats, and often lower than that expected from body size. Some species of parrots that live in desert regions of Australia have evolved mechanisms that reduce EWL, but this does not involve a reduction in BMR. In the field, parrots living in Western Australia had a lower water influx than predicted for nonpasserines, but this did not approach the value often found in other desert-adapted species. Values for the water economy index (water flux in free-living animals relative to their energy metabolism) were among the lowest that have been reported for desert-adapted birds.

Water balance of field-excavated aestivating Australian desert frogs, the cocoon-forming Neobatrachus aquilonius and the non-cocooning Notaden nichollsi (Amphibia: Myobatrachidae)

Publisher: The Company of Biologists

Date: 09-2006

DOI: 10.1242/JEB.02393

Abstract: Burrowed aestivating frogs of the cocoon-forming species Neobatrachus aquilonius and the non-cocooning species Notaden nichollsi were excavated in the Gibson Desert of central Australia. Their hydration state(osmotic pressure of the plasma and urine) was compared to the moisture content and water potential of the surrounding soil. The non-cocooning N. nichollsi was consistently found in sand dunes. While this sand had favourable water potential properties for buried frogs, the considerable spatial and temporal variation in sand moisture meant that frogs were not always in positive water balance with respect to the surrounding soil. The cocoon-forming N. aquilonius was excavated from two distinct habitat types, a claypan in which frogs had a well-formed cocoon and a dune swale where frogs did not have a cocoon. Cocoons of excavated frogs ranged in thickness from 19.4 μm to 55.61 μm and consisted of 81-229 layers. Cocooned claypan N. aquilonius were nearing exhaustion of their bladder water reserves and had a urine osmolality approaching that of the plasma. By contrast, non-cocooned N. aquilonius from the dune swale were fully hydrated, although soil moisture levels were not as high as calculated to be necessary to maintain water balance. Both species had similar plasma arginine vasotocin (AVT) concentrations ranging from 9.4 to 164 pg ml-1, except for one cocooned N. aquilonius with a higher concentration of 394 pg ml-1. For both species, AVT showed no relationship with plasma osmolality over the lower range of plasma osmolalities but was appreciably increased at the highest osmolality recorded. This study provides the first evidence that cocoon formation following burrowing is not obligatory in species that are capable of doing so, but that cocoon formation occurs when soil water conditions are more desiccating than for non-cocooned frogs.

Influence of season and weather on activity patterns of the numbat (Myrmecobius fasciatus) in captivity

Publisher: CSIRO Publishing

Date: 2004

DOI: 10.1071/ZO04038

Abstract: To separate the influence of weather from predation pressure and food availability, and to aid in the interpretation of activity data for wild numbats, we examined the influence of season and weather on the activity of captive numbats. Unlike other Australian marsupials, numbats are exclusively diurnal, being active for an average of 21.2% of the 24 h day. However, in the present study, activity duration varied seasonally, with numbats being active for longer periods in summer (39–65% of the available daylight) than winter (17–59%). During winter, captive numbats were active for shorter periods than wild numbats (presumably because captive numbats don't have to forage for food) however, they did not cease activity in the middle of the day during summer (suggesting that the inactivity of wild numbats at midday during summer is a response to food availability rather than a thermoregulatory response). Captive numbats were more active in summer than in winter, which may reflect their summer breeding season. Environmental conditions significantly affected daily activity, with low levels of activity recorded on days of low light intensity and high relative humidity. The majority of numbat activity occurred at ambient temperatures below thermoneutrality ( °C). The associated costs of thermoregulation for active numbats were calculated, from activity time, to be higher in winter (0.586 mL O2 g–1 h–1) than in summer (0.274 mL O2�g–1�h–1).

Physiological implications of climate change for a critically endangered Australian marsupial

Publisher: CSIRO Publishing

Date: 19-11-2020

DOI: 10.1071/ZO20067

Abstract: Extreme weather events (e.g. heatwaves and droughts) can expose animals to environmental conditions outside of their zones of physiological tolerance, and even resistance, and impact long-term viability of populations and species. We examined the thermal and hygric physiology of the critically endangered western ringtail possum (Pseudocheirus occidentalis), a member of a family of marsupial folivores (Pseudocheiridae) that appear particularly vulnerable to environmental extremes. Basal metabolic rate and other standard physiological variables measured at an ambient temperature of 30°C conformed to values for other marsupials. At lower temperatures, body temperature decreased slightly, and metabolic rate increased significantly at 5°C. At higher temperatures, possums experienced mild hyperthermia and increased evaporative heat loss by licking rather than panting. Their point of relative water economy (–8.7°C) was more favourable than other pseudocheirid possums and the koala (Phascolarctos cinereus). We predict that western ringtail possums should tolerate low ambient temperatures well and be more physiologically tolerant of hot and dry conditions than common (Pseudocheirus peregrinus) and particularly green (Pseudochirops archeri) ringtail possums, and koalas. Our physiological data can be incorporated into mechanistic species distribution models to test our hypothesis that western ringtail possums should physiologically tolerate the climate of habitat further inland than their current distribution, and withstand moderate impacts of climate change in the south-west of Western Australia.

Lizard tricks: Overcoming conflicting requirements of speed versus climbing ability by altering biomechanics of the lizard stride

Publisher: The Company of Biologists

Date: 2013

DOI: 10.1242/JEB.089060

Abstract: Adaptations promoting greater performance in one habitat are thought to reduce performance in others. However, there are many ex les of where, despite habitat differences, such predicted differences in performance do not occur. One such ex le is the relationship between locomotory performance to habitat for varanid lizards. To explain the lack of difference in locomotor performance we examined detailed observation of the kinematics of each lizard's stride. Differences in kinematics were greatest between climbing and non-climbing species. For terrestrial lizards, the kinematics indicated that increased femur adduction, femur rotation and ankle angle all contributed positively to changes in stride length, but they were constrained for climbing species, probably due to biomechanical restrictions on the centre of mass height (to increase stability on vertical surfaces). Despite climbing species having restricted stride length, no differences have been previously reported in sprint speed between climbing and non-climbing varanids. This is best explained by climbing varanids using an alternative speed modulation strategy of varying stride frequency to avoid the potential trade-off of speed vs stability on vertical surfaces. Thus, by measuring the relevant biomechanics for lizard strides, we have shown how kinematic differences among species can mask performance differences typically associated with habitat variation.

Some costs of reproduction for male bushcrickets, Requena verticalis (Orthoptera : Tettigoniidae) allocating resources to mate attraction and nuptial feeding

Publisher: Springer Science and Business Media LLC

Date: 07-1992

DOI: 10.1007/BF00167816

Field metabolic rate and water turnover of the numbat ( Myrmecobius fasciatus )

Publisher: Springer Science and Business Media LLC

Date: 11-2003

DOI: 10.1007/S00360-003-0380-6

Abstract: The numbat (Myrmecobius fasciatus) is a diurnal and exclusively termitivorous marsupial. This study examines interrelationships between diet, metabolic rate and water turnover for wild, free-living numbats. The numbats (488+/-20.8 g) remained in mass balance during the study. Their basal metabolic rate (BMR) was 3.6 l CO(2) day(-1), while their field metabolic rate (FMR) was 10.8+/-1.22 l CO(2) day(-1) (269+/-30.5 kJ day(-1)). The ratio FMR/BMR was 3+/-0.3 for numbats. We suggest that the most accurate way to predict the FMR of marsupials is from the regression log FMR=0.852 log BMR+0.767 ( r(2)=0.97). The FMR of the numbat was lower than, but not significantly different from, that of a generalised marsupial, both before (76%) and after (62-69%) correction for the significant effect of phylogeny on FMR. However the numbat's FMR is more comparable with that of other arid-habitat Australia marsupials (98-135%), for which the regression relating mass and FMR is significantly lower than for nonarid-habitat marsupials, independent of phylogeny. The field water turnover rate (FWTR) of free-living numbats (84.1 ml H(2)O day(-1)) was highly correlated with FMR, and was typical (89-98%) of that for an arid-habitat marsupial after phylogenetic correction. The higher than expected water economy index for the numbat (FWTR/FMR=0.3+/-0.03) suggests that either the numbats were drinking during the study, the water content of their diet was high, or the digestibility of their termite diet was low. Habitat and phylogenetic influences on BMR and FMR appear to have pre-adapted the numbat to a low-energy termitivorous niche.

Termite Digestibility and Water and Energy Contents Determine the Water Economy Index of Numbats (Myrmecobius fasciatus) and Other Myrmecophages

Publisher: University of Chicago Press

Date: 07-2004

DOI: 10.1086/421750

Hypothermia versus torpor in response to cold stress in the native Australian mouse Pseudomys hermannsburgensis and the introduced house mouse Mus musculus

Publisher: Elsevier BV

Date: 11-2007

DOI: 10.1016/J.CBPA.2007.08.013

Abstract: This study compared torpor as a response to food deprivation and low ambient temperature for the introduced house mouse (Mus musculus) and the Australian endemic sandy inland mouse (Pseudomys hermannsburgensis). The house mouse (mass 13.0+/-0.48 g) had a normothermic body temperature of 34.0+/-0.20 degrees C at ambient temperatures from 5 degrees C to 30 degrees C and a basal metabolic rate at 30 degrees C of 2.29+/-0.07 mL O2 g(-1) h(-1). It used torpor with spontaneous arousal at low ambient temperatures body temperature during torpor was 20.5+/-3.30 degrees C at 15 degrees C. The sandy inland mouse (mass 11.7+/-0.16 g) had a normothermic T(b) of 33.0+/-0.38 degrees C between T(a) of 5 degrees C to 30 degrees C, and a BMR of 1.45+/-0.26 mL O2 g(-1) h(-1) at 30 degrees C. They became hypothermic at low T(a) (T(b) about 17.3 degrees C at T(a)=15 degrees C), but did not spontaneously arouse. They did, however, survive and become normothermic if returned to room temperature (23 degrees C). We conclude that this is hypothermia, not torpor. Consequently, house mice (Subfamily Murinae) appear to use torpor as an energy conservation strategy whereas sandy inland mice (Subfamily Conilurinae) do not, but can survive hypothermia. This may reflect a general phylogenetic pattern of metabolic reduction in rodents. On the other hand, this may be related to differences in the social structure of house mice (solitary) and sandy inland mice (communal).

Is body shape of varanid lizards linked with retreat choice?

Publisher: CSIRO Publishing

Date: 2008

DOI: 10.1071/ZO08030

Abstract: In our earlier analysis of Varanus body shape, size was a dominating factor with some qualitative phylogenetic patterns and grouping of species into ecological categories. With a phylogeny and an improved capacity to account for the effects of size, we have reanalysed our morphometric data for male Australian goannas (Varanus spp.) using an increased number of specimens and species to examine whether variations in body shape can be accounted for by retreat choice, as it can for Western Australian Ctenophorus dragon lizards. After accounting for body size in the current analysis, four ecotypes based on retreat choice (i.e. those that retreat to oblique crevices between large rocks or rock faces, those that retreat to burrows dug into the ground, those that retreat to spaces under rocks or in tree hollows, and those that retreat to trees but not tree hollows) accounted for much of the variation in body shape. There is a phylogenetic pattern to the ecotypes, but accounting for phylogenetic effects did not weaken the link between body shape and ecotype based on retreat choice. This suggests that there are large differences in body shape among ecotypes, and shape is relatively independent of phylogeny. The strong link between shape and choice of retreat site in Varanus spp. is consistent with that for Ctenophorus spp. We speculate on why there might be a strong link between retreat choice and body shape for both Varanus and Ctenophorus.

Postural, pilo-erective and evaporative thermal windows of the short-beaked echidna ( Tachyglossus aculeatus )

Publisher: The Royal Society

Date: 2023

DOI: 10.1098/RSBL.2022.0495

Abstract: We identify for wild, free-living short-beaked echidnas ( Tachyglossus aculeatus ) a novel evaporative window, along with thermal windows, and demonstrate the insulating properties of the spines, using infrared thermography. The moist tip of their beak, with an underlying blood sinus, functions as a wet bulb globe thermometer, maximizing evaporative heat loss via an evaporative window. The ventral surface and insides of the legs are poorly insulated sites that act as postural thermal windows, while the spines provide flexible insulation (depending on piloerection). These avenues of heat exchange likely contribute to the higher-than-expected thermal tolerance of this species. Our study highlights how technological advances that allow for non-contact measurement of thermal variables allow us to better understand the physiological capacity of animals in their natural environment.

Thermoregulation by an Australian murine rodent, the ash-grey mouse (Pseudomys albocinereus)

Publisher: Elsevier BV

Date: 11-2012

DOI: 10.1016/J.CBPA.2012.07.011

Abstract: We examine here the thermal physiology of the ash-grey mouse, as there is a paucity of data to explain how Australian rodents meet thermoregulatory demands. Most ash-grey mice remained normothermic over a range of ambient temperatures (10 °C to 30 °C), although they became hyperthermic at high ambient temperatures. One in idual entered torpor at ambient temperatures of 20 °C and 25 °C, with minimal body temperatures of 24.5 °C and 28.4 °C respectively, before spontaneously arousing. This is the first evidence of torpor use by an Australian murine rodent. Our data suggest that although ash-grey mice have the physiological ability to use torpor, it is used rarely, presumably due to other behavioural and physiological adaptations. Their higher-than-expected basal metabolic rate (1.56±0.25 mL O(2)g(-1) h(-1)) indicates that ash-grey mice do not have a frugal approach to energy expenditure. Other standard physiological variables were typical of a generalised rodent. A readily-available omnivorous diet, nocturnal activity, semi-fossorial habit and social behaviour presumably allow a high energy lifestyle. A reluctance to use torpor, despite an apparent physiological ability to do so, supports the idea that the use of torpor reflects a net balance between the costs and benefits of a heterothermic thermoregulatory strategy.

Comparative physiology of Australian quolls (Dasyurus; Marsupialia)

Publisher: Springer Science and Business Media LLC

Date: 09-03-2010

DOI: 10.1007/S00360-010-0452-3

Abstract: Quolls (Dasyurus) are medium-sized carnivorous dasyurid marsupials. Tiger (3,840 g) and eastern quolls (780 g) are mesic zone species, northern quolls (516 g) are tropical zone, and chuditch (1,385 g) were once widespread through the Australian arid zone. We found that standard physiological variables of these quolls are consistent with allometric expectations for marsupials. Nevertheless, inter-specific patterns amongst the quolls are consistent with their different environments. The lower T (b) of northern quolls (34 degrees C) may provide scope for adaptive hyperthermia in the tropics, and they use torpor for energy/water conservation, whereas the larger mesic species (eastern and tiger quolls) do not appear to. Thermolability varied from little in eastern (0.035 degrees C degrees C(-1)) and tiger quolls (0.051 degrees C degrees C(-1)) to substantial in northern quolls (0.100 degrees C degrees C(-1)) and chuditch (0.146 degrees C degrees C(-1)), reflecting body mass and environment. Basal metabolic rate was higher for eastern quolls (0.662 +/- 0.033 ml O(2) g(-1) h(-1)), presumably reflecting their naturally cool environment. Respiratory ventilation closely matched metabolic demand, except at high ambient temperatures where quolls hyperventilated to facilitate evaporative heat loss tiger and eastern quolls also salivated. A higher evaporative water loss for eastern quolls (1.43 +/- 0.212 mg H(2)O g(-1) h(-1)) presumably reflects their more mesic distribution. The point of relative water economy was low for tiger (-1.3 degrees C), eastern (-12.5 degrees C) and northern (+3.3) quolls, and highest for the chuditch (+22.6 degrees C). We suggest that these differences in water economy reflect lower expired air temperatures and hence lower respiratory evaporative water loss for the arid-zone chuditch relative to tropical and mesic quolls.

Thermal and hygric physiology of Australian burrowing mygalomorph spiders (Aganippe spp.)

Publisher: Springer Science and Business Media LLC

Date: 22-08-2012

DOI: 10.1007/S00360-012-0681-8

Abstract: This study investigated the standard metabolic rate (SMR) and evaporative water loss (EWL) responses of three Australian trapdoor-constructing mygalomorph spider species, two undescribed arid-zone species (Aganippe 'Tropicana A' and A. 'Tropicana B') and a mesic-dwelling species (A. rhaphiduca) to acute environmental regimes of temperature and relative humidity. There were significant effects of species, temperature, and relative humidity on SMR. SMR was lower for A. raphiduca than both A. 'Tropicana' spp. with no difference between the two A. 'Tropicana' spp. Metabolic rate increased at higher temperature and relative humidity for all three species. There were significant effects of species, temperature, and relative humidity on EWL. The mesic Aganippe species had a significantly higher EWL than either arid Tropicana species. EWL was significantly higher at lower relative humidity. Our results suggest an environmental effect on EWL but not SMR, and that mygalomorphs are so vulnerable to desiccation that the burrow provides a crucial refuge to ameliorate the effects of low environmental humidity. We conclude that mygalomorphs are highly susceptible to disturbance, and are of high conservation value as many are short-range endemics.

Re-evaluating model assumptions suggests that Australian birds are more tolerant of heat and aridity than predicted: a response to Conradie et al. (2020)

Publisher: Oxford University Press (OUP)

Date: 2022

DOI: 10.1093/CONPHYS/COAC010

Abstract: Conradie et al. (2020) recently modelled the vulnerability of Australian arid birds to a changing climate. While the approach used by Conradie et al. (2020) is valuable, we argue that key assumptions in their study are poorly supported and the risks of a changing climate to arid zone avifauna are consequently overstated.

Geographical variation in the standard physiology of brushtail possums (Trichosurus): implications for conservation translocations

Publisher: Oxford University Press (OUP)

Date: 2018

DOI: 10.1093/CONPHYS/COY042

Environmental Correlates of Physiological Variables in Marsupials

Publisher: University of Chicago Press

Date: 05-2006

DOI: 10.1086/501063

Abstract: We analyzed body temperature (T(b)), basal metabolic rate (BMR), wet thermal conductance (C(wet)), and evaporative water loss (EWL) of marsupials by conventional and phylogenetically corrected regression. Allometric effects were substantial for BMR, C(wet), and EWL but not T(b). There was a strong phylogenetic signal for mass and all physiological traits. A significant phylogenetic signal remained for BMR, C(wet), and EWL even after accounting for the highly significant phylogenetic signal of mass. T(b), BMR, C(wet), and EWL allometric residuals were correlated with some diet, distribution, and climatic variables before and after correction for phylogeny. T(b) residuals were higher for marsupials from arid environments (high T(a) and more variable rainfall). The fossorial marsupial mole had a lower-than-expected T(b) residual. The allometric slope for BMR was 0.72-0.75. Residuals were consistently related to distribution aridity and rainfall variability, with species from arid and variable rainfall habitats having a low BMR, presumably to conserve energy in a low-productivity environment. The nectarivorous honey possum had a higher-than-expected BMR. For C(wet), the allometric slope was 0.55-0.62 residuals were related to diet, with folivores having low and insectivores high C(wet) residuals. The allometric slope for EWL was 0.68-0.73. EWL residuals were consistently correlated with rainfall variability, presumably facilitating maintenance of water balance during dry periods.

Patterns of body temperature variation and torpor in the numbat, Myrmecobius fasciatus (Marsupialia: Myrmecobiidae)

Publisher: Elsevier BV

Date: 08-2004

DOI: 10.1016/J.JTHERBIO.2004.05.003

Metabolic ecology of cockatoos in the south-west of Western Australia

Publisher: CSIRO Publishing

Date: 2002

DOI: 10.1071/ZO00067

Abstract: This study examined the metabolic ecology of six cockatoo taxa endemic to the south-west of Western Australia. As the availability of food is one factor that may influence the abundance and distribution of these cockatoos, we document here their baseline energy requirements and feeding patterns. Evaporative waterloss was also measured as this may correlate with the aridity of the species’ environment. Basal metabolic rate was significantly lower at 0.62 ± 0.13 mL O2 g–1 h–1 for the inland red-tailed black cockatoo than 1.11 ± 0.16 mL O2 g–1 h–1 for the forest red-tailed black cockatoo, but there was no significant difference in metabolic rate between the two white-tailed black cockatoos (0.86 ± 0.18 for Carnaby’s and 0.81 ± 0.11 mL O2 g–1 h–1 for Baudin’s) or the two corellas (0.95 ± 0.12 for Butler’s and 0.70 ± 0.04 mL O2 g–1 h–1 for Muir’s). There were no significant differences between the two white-tailed black cockatoos, and between the two corellas, with respect to evaporative water loss. The inland red-tailed black cockatoo had a significantly lower rate of evaporative water loss (0.44 ± 0.07 mg g–1 h–1) than the forest red-tailed black cockatoo (0.70 ± 0.06 mg g–1 h–1), which is presumably an adaptation to its more arid habitat. The total energy content of assorted native and introduced food items that form significant proportions of the diets for these cockatoos varied from only 0.17 kJ for a 9-mg Emex australis seed to 63.9 kJ for a 3-g Banksia attenuata nut. The energy content of each food item and the estimated daily energy requirements of the cockatoos enabled the calculation of the numbers of nuts/cones/seeds required by each species for a day, which ranged from 11 B. attenuata nuts for a Carnaby’s cockatoo to 3592 Persoonia longifolia seeds for a forest red-tailed black cockatoo.

Kinematics, maximal metabolic rate, sprint and endurance for a slow-moving lizard, the thorny devil (Moloch horridus)

Publisher: CSIRO Publishing

Date: 2004

DOI: 10.1071/ZO04026

Abstract: Metabolic physiology, morphology, activity patterns, performance traits and movement kinematics are thought to have coevolved in lizards. We examined links between these parameters for the thorny devil (Moloch horridus), a morphologically and ecologically specialised agamid lizard (body mass ~30 g). It has a maximum sustainable metabolic rate (VO2max) of 0.99 mL O2 g–1 h–1 while running at a velocity of 0.11�m�sec–1 at 35°C. This VO2 is typical of that for other lizards (except varanids), but its burst speed (1.21�m�sec–1) is slower than for a typical agamid (e.g. Ctenophorus ornatus at 3.59 m sec–1) and its endurance is appreciably higher. The kinematic pattern of hind-limb movement for M. horridus is different to that of a 'typical' similar-sized agamid, Ctenophorus ornatus, which is a fast-moving lizard that shelters in rock crevices. It is also different to the ecologically equivalent Phrynosoma platyrhinos. The slow and erratic ventilation of M. horridus (2.3 breaths min–1) at its maximum sustainable aerobic running speed occurs when it stops running. This might be a consequence of the hypaxial muscles being used for both lung ventilation and locomotion, which might be impairing pulmonary ventilation when running, but might also contribute to its high endurance. M. horridus is metabolically typical of agamids, but its body shape, movement patterns and locomotory performance traits are different, and might have coevolved with its specialisation for eating ants.

Using A Priori Contrasts for Multivariate Repeated-Measures ANOVA to Analyze Thermoregulatory Responses of the Dibbler (Parantechinus apicalis; Marsupialia, Dasyuridae)

Publisher: University of Chicago Press

Date: 09-2011

DOI: 10.1086/661637

Abstract: Physiological studies often involve the repeated measurement of in iduals over a range of ordered categorical conditions, for ex le, varying ambient temperature. We illustrate here the use of a priori contrasts for multivariate repeated-measures ANOVA by analyzing the thermal responses of various physiological variables for a small marsupial, the dibbler (Parantechinus apicalis). Our analyses showed that dibblers conform closely to the Scholander-Irving model of endothermy. Body temperature was constant at low air temperatures, was 36.3 ± 0.24°C at thermoneutrality (30°C), and increased at 35°C. Metabolic rate decreased with increasing ambient temperature to a basal rate of 0.619 ± 0.036 mL O(2) g(-1) h(-1) at 30°C it extrapolated closely to thermoneutral body temperature. Increased oxygen demand at lower ambient temperature was met by increased respiratory minute volume, achieved by increased respiratory frequency and tidal volume oxygen extraction was constant at about 19%. Evaporative water loss and wet and dry thermal conductance increased markedly at high ambient temperatures but not sufficiently to maintain constant body temperature. Relative water economy was similar to that of other small marsupials, increasing linearly at lower air temperatures with a point of relative water economy of 20.3°C. We conclude that a priori contrasts provide a statistically appropriate and powerful analysis that can be used routinely to statistically describe the pattern of response of physiological variables to a categorical factor and are especially useful for repeated-measures ANOVA designs common to many physiological studies.

Effect of Sampling Regime on Estimation of Basal Metabolic Rate and Standard Evaporative Water Loss Using Flow‐Through Respirometry

Publisher: University of Chicago Press

Date: 03-2010

DOI: 10.1086/605612

Abstract: Strict criteria have been established for measurement of basal metabolic rate and standard evaporative water loss to ensure that data can be compared intra- and interspecifically. However, data-s ling regimes vary, from essentially continuous s ling to interrupted (switching) systems with data recorded periodically at more widely spaced intervals. Here we compare one continuous and three interrupted s ling regimes to determine whether s ling regime has a significant effect on estimation of basal metabolic rate or standard evaporative water loss. Compared to continuous 20-s s ling averaged over 20 min, s ling every 6 min and averaging over 60 min overestimated basal metabolic rate and evaporative water loss, s ling every 3 min and averaging over 21 min underestimated basal metabolic rate, and s ling every 12 min and averaging over 36 min showed no difference in estimates. Increasing the period over which the minimum mean was calculated significantly increased estimates of physiological variables. Reducing the frequency of s ling from 20 s to a longer interval of 3, 6, or 12 min underestimated basal metabolic rate but not evaporative water loss. This indicates that s ling frequency per se influences estimates of basal metabolic rate and that differences are not just an artifact of differences in the period over which the mean is calculated. S ling regime can have a highly significant influence on estimation of standard physiological variables, although the actual differences between s ling regimes were generally small (usually <5%). Although continuous s ling is the preferred s ling regime for open-flow respirometry studies, if time and cost are prohibitive, then use of an appropriate switching system will result in smaller errors than measuring in iduals continuously for shorter periods.

Sera from patients with systemic lupus erythematosus demonstrate enhanced IgG binding to endothelial cells pretreated with tumour necrosis factor alpha

Publisher: Springer Science and Business Media LLC

Date: 09-1995

DOI: 10.1007/BF00302125

Metabolic, Ventilatory, and Hygric Physiology of the Gracile Mouse Opossum (Gracilinanus agilis)

Publisher: University of Chicago Press

Date: 03-2009

DOI: 10.1086/595967

Abstract: We present the first complete study of basic laboratory-measured physiological variables (metabolism, thermoregulation, evaporative water loss, and ventilation) for a South American marsupial, the gracile mouse opossum (Gracilinanus agilis). Body temperature (T(b)) was thermolabile below thermoneutrality (T(b) = 33.5 degrees C), but a substantial gradient between T(b) and ambient temperature (T(a)) was sustained even at T(a) = 12 degrees C (T(b) = 30.6 degrees C). Basal metabolic rate of 1.00 mL O2 g(-1) h(-1) at T(a) = 30 degrees C conformed to the general allometric relationship for marsupials, as did wet thermal conductance (5.7 mL O2 g(-1) h(-1) degrees C(-1)). Respiratory rate, tidal volume, and minute volume at thermoneutrality matched metabolic demand such that O2 extraction was 12.4%, and ventilation increased in proportion to metabolic rate at low T(a). Ventilatory accommodation of increased metabolic rate at low T(a) was by an increase in respiratory rate rather than by tidal volume or O2 extraction. Evaporative water loss at the lower limit of thermoneutrality conformed to that of other marsupials. Relative water economy was negative at thermoneutrality but positive below T(a) = 12 degrees C. Interestingly, the Neotropical gracile mouse opossums have a more positive water economy at low T(a) than an Australian arid-zone marsupial, perhaps reflecting seasonal variation in water availability for the mouse opossum. Torpor occurred at low T(a), with spontaneous arousal when T(b) > 20 degrees C. Torpor resulted in absolute energy and water savings but lower relative water economy. We found no evidence that gracile mouse opossums differ physiologically from other marsupials, despite their Neotropical distribution, sympatry with placental mammals, and long period of separation from Australian marsupials.

Use of Particle Tracking to Determine Optimal Release Dates and Locations for Rehabilitated Neonate Sea Turtles

Publisher: Frontiers Media SA

Date: 13-06-2017

DOI: 10.3389/FMARS.2017.00173

Two lines of evidence for physiological control of insensible evaporative water loss by a tiny marsupial

Publisher: The Company of Biologists

Date: 2020

DOI: 10.1242/JEB.234450

Abstract: We present two independent lines of evidence that a tiny dasyurid marsupial, the ningaui (Ningaui spp.), has acute physiological control of its insensible evaporative water loss below and within thermoneutrality. Perturbation of the driving force for evaporation by varying relative humidity, and therefore the water vapour pressure deficit between the animal and the ambient air, does not have the expected physical effect on evaporative water loss. Exposure to a helox atmosphere also does not have the expected physical effect of increasing on evaporative water loss for live ningauis (despite it having the expected effect of increasing heat loss for live ningauis), and increasing evaporative water loss for dead ningauis. We discuss the relative advantages and disadvantages of both experimental approaches for demonstrating physiological control of insensible evaporative water loss. An appreciation of physiological control is important because insensible evaporative water loss contributes to both water and heat balance, is clearly under environmental selection pressure, and potentially impacts the distribution of endotherms and their response to environmental change.

Are day-active small mammals rare and small birds abundant in Australian desert environments because small mammals are inferior thermoregulators?

Publisher: CSIRO Publishing

Date: 2004

DOI: 10.1071/AM04117

Abstract: Small desert birds are typically diurnal and highly mobile (hence conspicuous) whereas small non-volant mammals are generally nocturnal and less mobile (hence inconspicuous). Birds are more mobile than terrestrial mammals on a local and geographic scale, and most desert birds are not endemic but simply move to avoid the extremes of desert conditions. Many small desert mammals are relatively sedentary and regularly use physiological adjustments to cope with their desert environment (e.g., aestivation or hibernation). It seems likely that prey activity patterns and reduced conspicuousness to predators have reinforced nocturnality in small desert mammals. Differences such as nocturnality and mobility simply reflect differing life-history traits of birds and mammals rather than being a direct result of their differences in physiological capacity for tolerating daytime desert conditions.

Physiological regulation of evaporative water loss in endotherms: is the little red kaluta (Dasykaluta rosamondae) an exception or the rule?

Publisher: The Royal Society

Date: 07-06-2014

DOI: 10.1098/RSPB.2014.0149

Abstract: It is a central paradigm of comparative physiology that the effect of humidity on evaporative water loss (EWL) is determined for most mammals and birds, in and below thermoneutrality, essentially by physics and is not under physiological regulation. Fick's law predicts that EWL should be inversely proportional to ambient relative humidity (RH) and linearly proportional to the water vapour pressure deficit (Δwvp) between animal and air. However, we show here for a small dasyurid marsupial, the little kaluta ( Dasykaluta rosamondae ), that EWL is essentially independent of RH (and Δwvp) at low RH (as are metabolic rate and thermal conductance). These results suggest regulation of a constant EWL independent of RH, a hitherto unappreciated capacity of endothermic vertebrates. Independence of EWL from RH conserves water and heat at low RH, and avoids physiological adjustments to changes in evaporative heat loss such as thermoregulation. Re-evaluation of previously published data for mammals and birds suggests that a lesser dependence of EWL on RH is observed more commonly than previously thought, suggesting that physiological independence of EWL of RH is not just an unusual capacity of a few species, such as the little kaluta, but a more general capability of many mammals and birds.

Metabolic rate and endurance capacity in Australian varanid lizards (Squamata; Varanidae; Varanus)

Publisher: Oxford University Press (OUP)

Date: 23-06-2009

DOI: 10.1111/J.1095-8312.2009.01207.X

Effect of season on thermoregulation, metabolism and ventilation of the southern brown bandicootIsoodon obesulus (Marsupialia: Peramelidae)

Publisher: Wiley

Date: 2008

DOI: 10.1002/JEZ.448

Abstract: Seasonal variation in various thermoregulatory, metabolic and ventilatory parameters was examined for southern brown bandicoots (Isoodon obesulus fusciventer) from a Mediterranean climate near Perth, Western Australia. There was significant seasonal variation over the four annual seasons at thermoneutrality (Ta=30 degrees C) in body temperature, oxygen consumption, carbon dioxide production, respiratory exchange ratio, total evaporative water loss, wet and dry thermal conductance and tidal volume but not mass, ventilatory frequency, minute volume or oxygen extraction efficiency. Only carbon dioxide production and respiratory exchange ratio showed an annual pattern that was significantly related to season, with both being significantly higher in winter, presumably as a result of greater and higher quality food availability.

Control of insensible evaporate water loss by two species of mesic parrot suggests a thermoregulatory role

Publisher: The Company of Biologists

Date: 2020

DOI: 10.1242/JEB.229930

Abstract: Insensible evaporative water loss at or below thermoneutrality is generally assumed to be a passive physical process. However, some arid zone mammals and a single arid-zone bird can control their insensible water loss, so we tested the hypothesis that the same is the case for two parrot species from a mesic habitat. We investigated red-rumped parrots (Psephotus haematonotus) and eastern rosellas (Platycercus eximius), measuring their evaporative water loss, and other physiological variables, at a range of relative humidities at ambient temperatures of 20 and 30°C (below and at thermoneutrality). We found that, despite a decrease in evaporative water loss with increasing relative humidity, rates of evaporative water loss were not fully accounted for by the water vapour deficit between the animal and its environment, indicating that the insensible evaporative water loss of both parrots was controlled. It is unlikely that this deviation from physical expectations was regulation with a primary role for water conservation because our mesic-habitat parrots had equivalent regulatory ability as the arid-habitat budgerigar (Melopsittacus undulatus). This, together with our observations of body temperature and metabolic rate, instead support the hypothesis that acute physiological control of insensible water loss serves a thermoregulatory purpose for endotherms. Modification of both cutaneous and respiratory avenues of evaporative may be involved, possibly via modification of expired air temperature and humidity, and surface resistance.

Metabolic, ventilatory, and hygric physiology of a South American marsupial, the long-furred woolly mouse opossum

Publisher: Oxford University Press (OUP)

Date: 17-02-2010

DOI: 10.1644/09-MAMM-A-138R.1

The Field Metabolic Rate, Water Turnover, and Feeding and Drinking Behavior of a Small Avian Desert Granivore During a Summer Heatwave

Publisher: Frontiers Media SA

Date: 20-11-2019

DOI: 10.3389/FPHYS.2019.01405

Thermoregulatory, metabolic and ventilatory physiology of the western barred bandicoot (Perameles bougainville bougainville) in summer and winter

Publisher: CSIRO Publishing

Date: 2006

DOI: 10.1071/ZO05072

Abstract: The metabolic, thermoregulatory and ventilatory physiology of western barred bandicoots (Perameles bougainville bougainville), measured in the laboratory during summer and winter at ambient temperatures of 10 and 30°C, is relatively unusual for a peramelid marsupial. It has a low thermoneutral body temperature (33.7 ± 0.2°C), a very high basal metabolic rate (0.68 ± 0.03 mL O2 g–1 h–1 at ambient temperature = 30°C), low respiratory exchange ratios (often less than 0.7) and a high thermal conductance, reflecting its high oxygen consumption rate and low body temperature. Ventilatory frequency and tidal volume were variable between seasons, although minute volume and oxygen extraction efficiency were not. Minute volume of the western barred bandicoot was higher than expected, reflecting its high metabolic rate. Time of year (i.e. season) had an effect on some aspects of metabolic, thermoregulatory and ventilatory physiology (carbon dioxide production, respiratory exchange ratio, total evaporative water loss), but this effect was not as substantial nor as general as the effect of ambient temperature.

Thermoregulatory, metabolic and ventilatory physiology of the eastern barred bandicoot (Perameles gunnii)

Publisher: CSIRO Publishing

Date: 2006

DOI: 10.1071/ZO05071

Abstract: Thermoregulatory, metabolic and ventilatory parameters measured for the Tasmanian eastern barred bandicoot (Perameles gunnii) in thermoneutrality (ambient temperature = 30°C) were: body temperature 35.1°C, basal metabolic rate 0.55 mL O2 g–1 h–1, wet thermal conductance 2.2 mL O2 g–1 h–1 °C–1, dry thermal conductance 1.4 J g–1 h–1 °C–1, ventilatory frequency 24.8 breaths min–1, tidal volume 9.9 mL, minute volume of 246 mL min–1, and oxygen extraction efficiency 22.2%. These physiological characteristics are consistent with a cool/wet distribution, e.g. high basal metabolic rate (3.33 mL O2 g–0.75 h–1) for thermogenesis, low thermal conductance (0.92 J g–1 h–1 °C–1 at 10°C) for heat retention and intolerance of high ambient temperatures (≥35°C) with panting, hyperthermia and high total evaporative water loss (16.9 mg H2O g–1 h–1).

Metabolic, ventilatory and hygric physiology of the chuditch (Dasyurus geoffroii; Marsupialia, Dasyuridae)

Publisher: Elsevier BV

Date: 09-2009

DOI: 10.1016/J.CBPA.2009.05.002

Abstract: The chuditch is a large carnivorous dasyurid marsupial. Historically it had one of the widest geographical distributions of all marsupials, encompassing much of arid Australia, but it is now restricted to the mesic south-west of Western Australia. It is therefore of interest to determine if its physiology better reflects adaptation to its historically arid or present mesic habitat. The basic physiological parameters of the chuditch conform to other marsupials. Body mass of males (1385 g) was >400% of that predicted by phylogeny and this may be related to its carnivorous diet. Body temperature was 33.9 degrees C at ambient temperatures < or = thermoneutrality, with hyperthermia occurring above thermoneutrality. Basal metabolic rate was 0.361 mL O(2) g(-1) h(-1) at an ambient temperature of 31 degrees C. Metabolic rate increased below the thermoneutral zone by 0.038 mL O(2) g(-1) h(-1) degrees C(-1), and above the thermoneutral zone to 0.444+/-0.059 mL O(2) g(-1) h(-1) at 33.3 degrees C. Standard evaporative water loss was 0.498+/-0.071 mg g(-1) h(-1) at an ambient temperature of 26.0 degrees C, and increased at higher ambient temperatures due to panting and licking. Changes in wet thermal conductance largely reflected changes in evaporative heat loss, and dry thermal conductance increased at high ambient temperature due in part to posture change. Ventilatory parameters were consistent with metabolic demands in and below thermoneutrality, and suggested augmented evaporative heat loss above the thermoneutral zone. Chuditch had a high point of relative water economy of 22.6 degrees C, indicating favourable water economy at even moderate ambient temperatures, due to its low evaporative water loss rather than high metabolic water production. Chuditch were physiologically more similar to marsupials from arid rather than mesic habitats, better reflecting their historical distribution than their current geographical range.

Optimal body size with respect to maximal speed for the yellow-spotted monitor lizard (Varanus panoptes; varanidae)

Publisher: University of Chicago Press

Date: 05-2012

DOI: 10.1086/665275

Abstract: Studies of locomotor performance often link variation in morphology with ecology. While maximum sprint speed is a commonly used performance variable, the absolute limits for this performance trait are not completely understood. Absolute maximal speed has often been shown to increase linearly with body size, but several comparative studies covering a large range of body sizes suggest that maximal speed does not increase indefinitely with body mass but rather reaches an optimum after which speed declines. Because of the comparative nature of these studies, it is difficult to determine whether this decrease is due to biomechanical constraints on maximal speed or is a consequence of phylogenetic inertia or perhaps relaxed selection for lower maximal speed at large body size. To explore this issue, we have examined intraspecific variations in morphology, maximal sprint speed, and kinematics for the yellow-spotted monitor lizard Varanus panoptes, which varied in body mass from 0.09 to 5.75 kg. We show a curvilinear relationship between body size and absolute maximal sprint speed with an optimal body mass with respect to speed of 1.245 kg. This excludes the phylogenetic inertia hypothesis, because this effect should be absent intraspecifically, while supporting the biomechanical constraints hypothesis. The relaxed selection hypothesis cannot be excluded if there is a size-based behavioral shift intraspecifically, but the biomechanical constraints hypothesis is better supported from kinematic analyses. Kinematic measurements of hind limb movement suggest that the distance moved by the body during the stance phase may limit maximum speed. This limit is thought to be imposed by a decreased ability of the bones and muscles to support body mass for larger lizards.

Evolutionary relationships of sprint speed in Australian varanid lizards

Publisher: Wiley

Date: 21-07-2009

DOI: 10.1111/J.1469-7998.2009.00559.X

Spermatogenesis and plasma testosterone levels in Western Australian burrowing desert frogs, Cyclorana platycephala, Cyclorana maini, and Neobatrachus sutor, during aestivation

Publisher: Elsevier BV

Date: 03-2004

DOI: 10.1016/J.YGCEN.2003.12.005

Lactic Acid Bacteria Convert Glucosinolates to Nitriles Efficiently Yet Differently from Enterobacteriaceae

Publisher: American Chemical Society (ACS)

Date: 15-03-2013

DOI: 10.1021/JF305442J

Abstract: Glucosinolates from the genus Brassica can be converted into bioactive compounds known to induce phase II enzymes, which may decrease the risk of cancers. Conversion via hydrolysis is usually by the brassica enzyme myrosinase, which can be inactivated by cooking or storage. We examined the potential of three beneficial bacteria, Lactobacillus plantarum KW30, Lactococcus lactis subsp. lactis KF147, and Escherichia coli Nissle 1917, and known myrosinase-producer Enterobacter cloacae to catalyze the conversion of glucosinolates in broccoli extract. Enterobacteriaceae consumed on average 65% glucoiberin and 78% glucoraphanin, transforming them into glucoiberverin and glucoerucin, respectively, and small amounts of iberverin nitrile and erucin nitrile. The lactic acid bacteria did not accumulate reduced glucosinolates, consuming all at 30-33% and transforming these into iberverin nitrile, erucin nitrile, sulforaphane nitrile, and further unidentified metabolites. Adding beneficial bacteria to a glucosinolate-rich diet may increase glucosinolate transformation, thereby increasing host exposure to bioactives.

Adsorption and movement of water by skin of the Australian thorny devil (Agamidae:Moloch horridus)

Publisher: The Royal Society

Date: 09-2017

DOI: 10.1098/RSOS.170591

Abstract: Moisture-harvesting lizards, such as the Australian thorny devil Moloch horridus , have remarkable adaptations for inhabiting arid regions. Their microstructured skin surface, with channels in between overlapping scales, enables them to collect water by capillarity and passively transport it to the mouth for ingestion. We characterized this capillary water transport for live thorny devils using high-speed video analyses. Comparison with preserved specimens showed that live lizards are required for detailed studies of skin water transport. For thorny devils, there was no directionality in cutaneous water transport (unlike Phrynosoma ) as 7 µl water droplets applied to the skin were transported radially over more than 9.2 mm. We calculated the total capillary volume as 5.76 µl cm −2 (dorsal) and 4.45 µl cm −2 (ventral), which is reduced to 50% filling by the time transportation ceases. Using micro-computed tomography and scanning electron microscopy of shed skin to investigate capillary morphology, we found that the channels are hierarchically structured as a large channel between the scales that is sub- ided by protrusions into smaller sub-capillaries. The large channel quickly absorbs water whereas the sub-capillary structure extends the transport distance by about 39% and potentially reduces the water volume required for drinking. An adapted dynamics function, which closely reflects the channel morphology, includes that ecological role.

Metabolic, hygric and ventilatory physiology of the red-tailed phascogale (Phascogale calura; Marsupialia, Dasyuridae): Adaptations to aridity or arboreality?

Publisher: Springer Science and Business Media LLC

Date: 11-2013

DOI: 10.1016/J.MAMBIO.2012.11.008

Evolution of limb bone loading and body size in varanid lizards

Publisher: The Company of Biologists

Date: 15-09-2011

DOI: 10.1242/JEB.059345

Abstract: Geometric scaling predicts that stresses on limb bones and muscles should increase with body size. Mammals counter this size-related increase in stress partially through changes in bone geometry, but largely through changes in posture, with larger species having a more erect stance. However, the ability to counter size-related stresses in this fashion may be limited to those taxa that have a parasagittal gait (such as mammals), where legs are swung underneath the body. We examined locomotor kinematics for 11 species of varanid lizards (from 0.04 to 8 kg body mass) that have a sprawling gait, to determine how they moderate size-related stresses. Posture, as indicated by femur adduction and hip heights, did not change significantly with body size, beyond that expected from geometrical scaling. Instead, lizards mitigated size-related increases in stress by increasing duty factor and possibly reducing femur rotation. Incorporating these factors in biomechanical models predicted that both bending (∝M0.016, where M is mass) and torsional (∝M–0.049) stresses should be nearly independent of body size over the size range examined. However, increasing duty factor and reducing femur rotation probably have deleterious effects on speed, and this difference in kinematics with size may explain why speed scales lower for sprawling lizards than for parasagittal mammals (∝M0.17 and ∝M0.24, respectively). Further, paralleling conclusions for the synapsid lineage, these findings suggest that evolution from sprawling to upright posture did not occur in archosaurs as a response to larger size rather, these archosaurs likely became upright first and larger later.

Biophysical properties of the pelt of a diurnal marsupial, the numbat(Myrmecobius fasciatus), and its role in thermoregulation

Publisher: The Company of Biologists

Date: 15-08-2003

DOI: 10.1242/JEB.00484

Abstract: Numbats are unusual marsupials in being exclusively diurnal and termitivorous. They have a sparse (1921 hairs cm-2) and shallow(1.19 mm) pelt compared with other marsupials. Coat reflectivity is low (19%)for numbats compared with nocturnal marsupials, but absorptivity is similar to that of diurnal North American ground squirrels (72%), indicating that the coat of the numbat may be adapted for acquisition of solar heat. Numbat coat thermal resistance decreases significantly with wind speed from 45.9 s m-1 (at 0.5 m s-1) to 29.8 s m-1 (at 3 m s-1). Erecting the fur significantly increases pelt depth (6.5 mm)and coat resistance (79.2–64.2 s m-1) at wind speeds between 0.5 m s-1 and 3 m s-1. Numbat coat resistance is much lower than that of other marsupials, and wind speed has a greater influence on coat resistance for numbats than for other mammals, reflecting the low pelt density and thickness. Solar heat gain by numbats through the pelt to the level of the skin(60–63%) is similar to the highest value measured for any mammal. However the numbat's high solar heat gain is not associated with the same degree of reduction in coat resistance as seen for other mammals, suggesting that its pelt has structural and spectral characteristics that enhance both solar heat acquisition and endogenous heat conservation. Maximum solar heat gain is estimated to be 0.5–3.6 times resting metabolic heat production for the numbat at ambient temperatures of 15–32.5°C, so radiative heat gain is probably an important aspect of thermoregulation for wild numbats.

Coping with Thermal Challenges: Physiological Adaptations to Environmental Temperatures

Publisher: Wiley

Date: 07-2012

DOI: 10.1002/CPHY.C110055

Abstract: Temperature profoundly influences physiological responses in animals, primarily due to the effects on biochemical reaction rates. Since physiological responses are often exemplified by their rate dependency (e.g., rate of blood flow, rate of metabolism, rate of heat production, and rate of ion pumping), the study of temperature adaptations has a long history in comparative and evolutionary physiology. Animals may either defend a fairly constant temperature by recruiting biochemical mechanisms of heat production and utilizing physiological responses geared toward modifying heat loss and heat gain from the environment, or utilize biochemical modifications to allow for physiological adjustments to temperature. Biochemical adaptations to temperature involve alterations in protein structure that compromise the effects of increased temperatures on improving catalytic enzyme function with the detrimental influences of higher temperature on protein stability. Temperature has acted to shape the responses of animal proteins in manners that generally preserve turnover rates at animals' normal, or optimal, body temperatures. Physiological responses to cold and warmth differ depending on whether animals maintain elevated body temperatures (endothermic) or exhibit minimal internal heat production (ectothermic). In both cases, however, these mechanisms involve regulated neural and hormonal over heat flow to the body or heat flow within the body. Ex les of biochemical responses to temperature in endotherms involve metabolic uncoupling mechanisms that decrease metabolic efficiency with the outcome of producing heat, whereas ectothermic adaptations to temperature are best exemplified by the numerous mechanisms that allow for the tolerance or avoidance of ice crystal formation at temperatures below 0°C. © 2012 American Physiological Society. Compr Physiol 2:2151‐2202, 2012.

Fighting the ventilator - are fast rates an effective alternative to paralysis?

Publisher: Elsevier BV

Date: 04-1986

DOI: 10.1016/0378-3782(86)90007-1

Abstract: We investigated the effect of increased ventilator rates on the respiratory activity of 17 infants, all actively expiring against the ventilator at conventional rates. Fast rate ventilation was rarely associated with apnoea (3 babies only) and the infant's respiratory efforts even at rates of 120/min had an important effect on tidal exchange. Seven infants altered their respiratory response to breathe in synchrony with the ventilator at 60 breaths/min and 5 maintained this at 120 breaths/min. Nine of the 17 infants continued to actively expire against positive pressure inflation at 60 breaths/min and in two this persisted at 120/min, the remaining 7 infants showed incoordinated breathing at that rate. We conclude that fast rate ventilation appears to have only limited success in suppressing respiratory activity in infants actively expiring against the ventilator.

Relative Water Economy Is a Useful Index of Aridity Tolerance for Australian Poephiline Finches

Publisher: MDPI AG

Date: 31-03-2022

DOI: 10.3390/BIRDS3020012

Abstract: We evaluate if the iconic Australian Zebra Finch (Taeniopygia guttata) has a unique physiology or if its metabolic, thermal and hygric physiology are similar to other Australian poephiline finches, by comparing it with three other species, the arid-habitat Painted Finch (Emblema pictum) and the mesic-habitat Double-barred (Taeniopygia bichenovii) and Red-browed (Neochmia temporalis) Finches. All physiological variables responded to ambient temperature as expected. There were no species differences for any of the standard physiological variables, consistent with the hypotheses that birds are pre-adapted to arid habitats, the recent development of Australian deserts has limited opportunity for physiological adaptation, and all four species share similar behavioural and ecological traits. Nevertheless, the ambient temperature where metabolic water production equals evaporative water loss (point of relative water economy) was highest for the Zebra (19.1 °C), lower for Double-barred (16.4 °C) and Painted (15.2 °C) and lowest for Red-Browed (4.1 °C) Finches, corresponding with their general patterns of habitat aridity. The point of relative water economy may be a sensitive index for assessing a species’ tolerance of aridity because it integrates in idual physiological variables. We conclude that the Zebra Finch is not a physiological outlier amongst Australian finches, but is at the end of a continuum of aridity tolerance for the four study species.

Measuring metabolic rates of small terrestrial organisms by fluorescence-based closed-system respirometry

Publisher: The Company of Biologists

Date: 2018

DOI: 10.1242/JEB.172874

Abstract: We explore a recent innovative variation of closed-system respirometry for terrestrial organisms, whereby pO2 is repeatedly measured fluorometrically in a constant-volume chamber over multiple time points. We outline a protocol that aligns this technology with the broader literature on aerial respirometry, including the calculations required to accurately convert O2 depletion to metabolic rate (MR). We identify a series of assumptions, and sources of error associated with this technique, including thresholds where O2 depletion becomes limiting, that impart errors to the calculation and interpretation of MR. Using these adjusted calculations, we found that the resting MR of five species of angiosperm seeds ranged from 0.011 to 0.640 mL.g−1.h−1, consistent with published seed MR. This innovative methodology greatly expands the lower size limit of terrestrial organisms that can be measured, and offers the potential for measuring MR changes over time as a result of physiological processes of the organism.

Gross renal morphology of the numbat (Myrmecobius fasciatus) (Marsupialia:Myrmecobiidae)

Publisher: CSIRO Publishing

Date: 2010

DOI: 10.1071/AM10005

Abstract: There is a strong correlation between the structure of the mammalian kidney and its urinary concentrating ability. We examine here the kidney of an endangered termitivorous marsupial (Myrmecobius fasciatus) and use the measured kidney morphometrics to calculate maximal urinary concentration. The relative medullary area (1.34) of the kidney of M. fasciatus is typical of other dasyuromorph marsupials, as is its predicted maximal urinary concentration of 3617 mOsm kg–1 H2O, despite its historically semiarid/arid distribution. The termitivorous diet of M. fasciatus presumably provides it with sufficient water to limit selection for a high urinary concentrating capacity.

Reappraisal of the comparative cost of human locomotion using gait-specific allometric analyses

Publisher: The Company of Biologists

Date: 15-10-2007

DOI: 10.1242/JEB.000992

Abstract: The alleged high net energy cost of running and low net energy cost of walking in humans have played an important role in the interpretation of the evolution of human bipedalism and the biomechanical determinants of the metabolic cost of locomotion. This study re-explores how the net metabolic energy cost of running and walking (J kg–1m–1) in humans compares to that of animals of similar mass using new allometric analyses of previously published data. Firstly, this study shows that the use of the slope of the regression between the rate of energy expenditure and speed to calculate the net energy cost of locomotion overestimates the net cost of human running. Also, the net energy cost of human running is only 17% higher than that predicted based on their mass. This value is not exceptional given that over a quarter of the previously examined mammals and birds have a net energy cost of running that is 17% or more above their allometrically predicted value. Using a new allometric equation for the net energy cost of walking, this study also shows that human walking is 20%less expensive than predicted for their mass. Of the animals used to generate this equation, 25% have a relatively lower net cost of walking compared with their allometrically predicted value. This new walking allometric analysis also indicates that the scaling of the net energy cost of locomotion with body mass is gait dependent. In conclusion, the net costs of running and walking in humans are moderately different from those predicted from allometry and are not remarkable for an animal of its size.

Phenophysiological variation of a bee that regulates hive humidity, but not hive temperature

Publisher: The Company of Biologists

Date: 2016

DOI: 10.1242/JEB.137588

Abstract: Seasonal acclimatisation of thermal tolerance, evaporative water loss and metabolic rate, along with regulation of the hive environment, are key ways whereby hive-based social insects mediate climatic challenges throughout the year, but the relative importance of these traits remains poorly understood. We examined seasonal variation in metabolic rate and evaporative water loss of worker bees, and seasonal variation of hive temperature and humidity, for the stingless bee Austroplebeia essingtoni (Apidae Meliponini) in arid tropical Australia. Both water loss and metabolic rate were lower in the cooler, dry winter than in the hot, wet summer at most ambient temperatures between 20°C and 45°C. Contrary to expectation, thermal tolerance thresholds were higher in the winter than in the summer. Hives were cooler in the cooler, dry winter than in the hot, wet summer, linked to an apparent lack of hive thermoregulation. The humidity of hives was regulated at approximately 65% RH in both seasons, which is higher than unoccupied control hives in the dry season, but less than unoccupied control hives in the wet season. While adaptations to promote water balance appear more important for survival of A. essingtoni than traits related to temperature regulation, their capacity for water conservation is coincident with increased thermal tolerance. For these small, eusocial stingless bees in the arid tropics, where air temperatures are relatively high and stable compared with temperate areas, regulation of hive humidity appears to be of more importance than temperature in maintaining hive health.

Sound production by the short‐beaked echidna (Tachyglossus aculeatus)

Publisher: Wiley

Date: 26-09-2023

DOI: 10.1111/JZO.13114

Discovery Projects - Grant ID: DP160103627

Start Date: 2016

End Date: 09-2021

Amount: $274,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP160100381

Start Date: 09-2016

End Date: 09-2019

Amount: $336,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0665044

Start Date: 2006

End Date: 02-2011

Amount: $175,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP0211988

Start Date: 10-2002

End Date: 04-2006

Amount: $67,635.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0209728

Start Date: 12-2002

End Date: 12-2005

Amount: $231,000.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP200200680

Start Date: 07-2021

End Date: 06-2025

Amount: $582,084.00

Funder: Australian Research Council