ORCID Profile
0000-0002-7289-9399
Current Organisation
Macquarie University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Zoology | Animal Neurobiology | Conservation And Biodiversity | Genetics | Animal Behaviour | Sensory Systems | Gene Expression | Sensory Systems | Neurobiology | Animal Anatomy And Histology | Neurosciences | Comparative Physiology | Ecology | Wildlife and Habitat Management | Evolutionary Biology | Evolutionary Impacts of Climate Change | Comparative Physiology | Animal Systematics, Taxonomy And Phylogeny | Marine And Estuarine Ecology (Incl. Marine Ichthyology) | Behavioural Ecology | Biological Adaptation
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Biological Sciences | Biological sciences | Natural Hazards in Marine Environments | Hearing, vision, speech and their disorders | Water Safety | Animal Welfare | Nervous System and Disorders | Expanding Knowledge in the Medical and Health Sciences | Living resources (incl. impacts of fishing on non-target species) | Integrated (ecosystem) assessment and management | Behavioural and cognitive sciences | Marine Flora, Fauna and Biodiversity | Other |
Related Links
Publications
Evolution of the eyes of vipers with and without infrared-sensing pit organs
Publisher: Oxford University Press (OUP)
Date: 10-03-2019
A shark's eye view: testing the ‘mistaken identity theory’ behind shark bites on humans
Publisher: The Royal Society
Date: 10-2021
Abstract: Shark bites on humans are rare but are sufficiently frequent to generate substantial public concern, which typically leads to measures to reduce their frequency. Unfortunately, we understand little about why sharks bite humans. One theory for bites occurring at the surface, e.g. on surfers, is that of mistaken identity, whereby sharks mistake humans for their typical prey (pinnipeds in the case of white sharks). This study tests the mistaken identity theory by comparing video footage of pinnipeds, humans swimming and humans paddling surfboards, from the perspective of a white shark viewing these objects from below. Videos were processed to reflect how a shark's retina would detect the visual motion and shape cues. Motion cues of humans swimming, humans paddling surfboards and pinnipeds swimming did not differ significantly. The shape of paddled surfboards and human swimmers was also similar to that of pinnipeds with their flippers abducted. The difference in shape between pinnipeds with abducted versus adducted flippers was bigger than between pinnipeds with flippers abducted and surfboards or human swimmers. From the perspective of a white shark, therefore, neither visual motion nor shape cues allow an unequivocal visual distinction between pinnipeds and humans, supporting the mistaken identity theory behind some bites.
Electrophysiological measures of temporal resolution, contrast sensitivity and spatial resolving power in sharks
Publisher: Springer Science and Business Media LLC
Date: 28-02-2017
DOI: 10.1007/S00359-017-1154-Z
Abstract: In most animals, vision plays an important role in detecting prey, predators and conspecifics. The effectiveness of vision in assessing cues such as motion and shape is influenced by the ability of the visual system to detect changes in contrast in both space and time. Understanding the role vision plays in shark behaviour has been limited by a lack of knowledge about their temporal resolution, contrast sensitivity and spatial resolution. In this study, an electrophysiological approach was used to compare these measures across five species of sharks: Chiloscyllium punctatum, Heterodontus portusjacksoni, Hemiscyllium ocellatum, Mustelus mustelus and Haploblepharus edwardsii. All shark species were highly sensitive to brightness contrast and were able to detect contrast differences as low as 1.6%. Temporal resolution of flickering stimuli ranged from 28 to 44 Hz. Species that inhabit brighter environments were found to have higher temporal resolution. Spatial resolving power was estimated in C. punctatum, H. portusjacksoni and H. ocellatum and ranged from 0.10 to 0.35 cycles per degree, which is relatively low compared to other vertebrates. These results suggest that sharks have retinal adaptations that enhance contrast sensitivity at the expense of temporal and spatial resolution, which is beneficial for vision in dimly lit and/or low contrast aquatic environments.
Multiple rod–cone and cone–rod photoreceptor transmutations in snakes: evidence from visual opsin gene expression
Publisher: The Royal Society
Date: 27-01-2016
Abstract: In 1934, Gordon Walls forwarded his radical theory of retinal photoreceptor ‘transmutation’. This proposed that rods and cones used for scotopic and photopic vision, respectively, were not fixed but could evolve into each other via a series of morphologically distinguishable intermediates. Walls' prime evidence came from series of diurnal and nocturnal geckos and snakes that appeared to have pure-cone or pure-rod retinas (in forms that Walls believed evolved from ancestors with the reverse complement) or which possessed intermediate photoreceptor cells. Walls was limited in testing his theory because the precise identity of visual pigments present in photoreceptors was then unknown. Subsequent molecular research has hitherto neglected this topic but presents new opportunities. We identify three visual opsin genes, rh1 , sws1 and lws , in retinal mRNA of an ecologically and taxonomically erse s le of snakes central to Walls' theory. We conclude that photoreceptors with superficially rod- or cone-like morphology are not limited to containing scotopic or photopic opsins, respectively. Walls' theory is essentially correct, and more research is needed to identify the patterns, processes and functional implications of transmutation. Future research will help to clarify the fundamental properties and physiology of photoreceptors adapted to function in different light levels.
Miniaturisation reduces contrast sensitivity and spatial resolving power in ants
Publisher: The Company of Biologists
Date: 2019
DOI: 10.1242/JEB.203018
Abstract: Vision is crucial for animals to find prey, locate conspecifics, and to navigate within cluttered landscapes. Animals need to discriminate objects against a visually noisy background. However, the ability to detect spatial information is limited by eye size. In insects, as in iduals become smaller, the space available for the eyes reduces, which affects the number of ommatidia, the size of the lens and the downstream information processing capabilities. The evolution of small body size in a lineage, known as miniaturisation, is common in insects. Here, using pattern electroretinography with vertical sinusoidal gratings as stimuli, we studied how miniaturisation affects spatial resolving power and contrast sensitivity in four diurnal ants that live in a similar environment but varied in their body and eye size. We found that ants with fewer and smaller ommatidial facets had lower spatial resolving power and contrast sensitivity. The spatial resolving power was maximum in the largest ant Myrmecia tarsata at 0.60 cycles per degree (cpd) compared to the ant with smallest eyes Rhytidoponera inornata that had 0.48 cpd. Maximum contrast sensitivity (minimum contrast threshold) in M. tarsata (2627 facets) was 15.51 (6.4% contrast detection threshold) at 0.1 cpd, while the smallest ant R. inornata (227 facets) had a maximum contrast sensitivity of 1.34 (74.1% contrast detection threshold) at 0.05 cpd. This is the first study to physiologically investigate contrast sensitivity in the context of insect allometry. Miniaturisation thus dramatically decreases maximum contrast sensitivity and also reduces spatial resolution, which could have implications for visually guided behaviours.
Electric Field Detection in Sawfish and Shovelnose Rays
Publisher: Public Library of Science (PLoS)
Date: 25-07-2012
Microspectrophotometry of visual pigments and oil droplets in a marine bird, the wedge-tailed shearwaterPuffinus pacificus: topographic variations in photoreceptor spectral characteristics
Publisher: The Company of Biologists
Date: 03-2004
DOI: 10.1242/JEB.00857
Abstract: Microspectrophotometric examination of the retina of a procellariiform marine bird, the wedge-tailed shearwater Puffinus pacificus, revealed the presence of five different types of vitamin A1-based visual pigment in seven different types of photoreceptor. A single class of rod contained a medium-wavelength sensitive visual pigment with a wavelength of maximum absorbance (λmax) at 502 nm. Four different types of single cone contained visual pigments maximally sensitive in either the violet(VS, λmax 406 nm), short (SWS, λmax 450 nm), medium (MWS, λmax 503 nm) or long (LWS,λ max 566 nm) spectral ranges. In the peripheral retina, the SWS, MWS and LWS single cones contained pigmented oil droplets in their inner segments with cut-off wavelengths (λcut) at 445 (C-type),506 (Y-type) and 562 nm (R-type), respectively. The VS visual pigment was paired with a transparent (T-type) oil droplet that displayed no significant absorption above at least 370 nm. Both the principal and accessory members of the double cone pair contained the same 566 nm λmax visual pigment as the LWS single cones but only the principal member contained an oil droplet, which had a λcut at 413 nm. The retina had a horizontal band or `visual streak' of increased photoreceptor density running across the retina approximately 1.5 mm dorsal to the top of the pecten. Cones in the centre of the horizontal streak were smaller and had oil droplets that were either transparent/colourless or much less pigmented than at the periphery. It is proposed that the reduction in cone oil droplet pigmentation in retinal areas associated with high visual acuity is an adaptation to compensate for the reduced photon capture ability of the narrower photoreceptors found there. Measurements of the spectral transmittance of the ocular media reveal that wavelengths down to at least 300 nm would be transmitted to the retina.
Multiple cone visual pigments and the potential for trichromatic colour vision in two species of elasmobranch
Publisher: The Company of Biologists
Date: 15-12-2004
DOI: 10.1242/JEB.01314
Abstract: Elasmobranchs (sharks, skates and rays) are the modern descendents of the first jawed vertebrates and, as apex predators, often occupy the highest trophic levels of aquatic (predominantly marine) ecosystems. However, despite their crucial role in the structure of marine communities, their importance both to commercial and to recreational fisheries, and the inherent interest in their role in vertebrate evolution, very little is known about their visual capabilities, especially with regard to whether or not they have the potential for colour vision. Using microspectrophotometry, we show that the retinae of the giant shovelnose ray (Rhinobatos typus) and the eastern shovelnose ray (Aptychotrema rostrata) contain three spectrally distinct cone visual pigments with wavelengths of maximum absorbance(λmax) at 477, 502 and 561 nm and at 459, 492 and 553 nm,respectively. The retinae of R. typus and A. rostrata also contain a single type of rod visual pigment with λmax at 504 and 498 nm, respectively. R. typus, living in the same estuarine waters as A. rostrata, were found to have identical visual pigments to R. typus inhabiting coral reef flats, despite a considerable difference in habitat spectral radiance. This is the first time that multiple cone visual pigments have been measured directly in an elasmobranch. The finding raises the possibility that some species are able to discriminate colour – a visual ability traditionally thought to be lacking in this vertebrate class – and it is evident that the visual ecology of elasmobranchs is far more complex than once thought.
Avian Visual Pigments: Characteristics, Spectral Tuning, and Evolution
Publisher: University of Chicago Press
Date: 2007
DOI: 10.1086/510141
Abstract: Birds are highly visual animals with complex visual systems. In this article, we discuss the spectral characteristics and genetic mechanisms of the spectral tuning of avian visual pigments. The avian retina contains a single type of rod, four spectrally distinct types of single cone, and a single type of double cone photoreceptor. Only the single cones are thought to be involved in color discrimination double cones are thought to be involved in achromatic visual tasks, such as movement detection and pattern recognition. Visual pigment opsin protein genes in birds are orthologous to those in other vertebrates and have a common origin early in vertebrate evolution. Mechanisms of spectral tuning in the different classes of avian cone visual pigments show similarities in most instances to those in other vertebrates. The exception is the ultraviolet/violet (SWS1) class of pigments phylogenetic evidence indicates that the ancestral vertebrate SWS1 pigment was ultraviolet sensitive (UVS), with different molecular mechanisms accounting for the generation of violet-sensitive (VS) pigments in different vertebrate classes. In birds, however, UVS visual pigments have re-evolved from an ancestral avian VS pigment by using a novel molecular mechanism not seen in other vertebrate classes. This has occurred independently in four of the 14 avian orders examined to date, although the adaptive significance of this is currently unknown.
Retinal topography and microhabitat diversity in a group of dragon lizards
Publisher: Wiley
Date: 17-10-2019
DOI: 10.1002/CNE.24780
Abstract: The well-studied phylogeny and ecology of dragon lizards and their range of visually mediated behaviors provide an opportunity to examine the factors that shape retinal organization. Dragon lizards consist of three evolutionarily stable groups based on their shelter type, including burrows, shrubs, and rocks. This allows us to test whether microhabitat changes are reflected in their retinal organization. We examined the retinae of three burrowing species (Ctenophorus pictus, C. gibba, and C. nuchalis), and three species that shelter in rock crevices (C. ornatus, C. decresii, and C. vadnappa). We used design-based stereology to s le both the photoreceptor array and neurons within the retinal ganglion cell layer to estimate areas specialized for acute vision. All species had two retinal specializations mediating enhanced spatial acuity: a fovea in the retinal center and a visual streak across the retinal equator. Furthermore, all species featured a dorsoventrally asymmetric photoreceptor distribution with higher photoreceptor densities in the ventral retina. This dorsoventral asymmetry may provide greater spatial summation of visual information in the dorsal visual field. Burrow-dwelling species had significantly larger eyes, higher total numbers of retinal cells, higher photoreceptor densities in the ventral retina, and higher spatial resolving power than rock-dwelling species. C. pictus, a secondary burrow-dwelling species, was the only species that changed burrow usage over evolutionary time, and its retinal organization revealed features more similar to rock-dwelling species than other burrow-dwelling species. This suggests that phylogeny may play a substantial role in shaping retinal organization in Ctenophorus species compared to microhabitat occupation.
Can the Dynamic Colouration and Patterning of Bluelined Goatfish (Mullidae; <b><i>Upeneichthys lineatus</i></b>) Be Perceived by Conspecifics?
Publisher: S. Karger AG
Date: 2021
DOI: 10.1159/000519894
Abstract: Bluelined goatfish ( i Upeneichthys lineatus /i ) exhibit dynamic body colour changes and transform rapidly from a pale, buff/white, horizontally banded pattern to a conspicuous, vertically striped, red pattern when foraging. This red pattern is potentially an important foraging signal for communication with conspecifics, provided that i U. lineatus /i can detect and discriminate the pattern. Using both physiological and behavioural experiments, we first examined whether i U. lineatus /i possess visual pigments with sensitivity to long (“red”) wavelengths of light, and whether they can discriminate the colour red. Microspectrophotometric measurements of retinal photoreceptors showed that while i U. lineatus /i lack visual pigments dedicated to the red part of the spectrum, their pigments likely confer some sensitivity in this spectral band. Behavioural colour discrimination experiments suggested that i U. lineatus /i can distinguish a red reward stimulus from a grey distractor stimulus of variable brightness. Furthermore, when presented with red stimuli of varying brightness they could mostly discriminate the darker and lighter reds from the grey distractor. We also obtained anatomical estimates of visual acuity, which suggest that i U. lineatus /i can resolve the contrasting bands of conspecifics approximately 7 m away in clear waters. Finally, we measured the spectral reflectance of the red and white colouration on the goatfish body. Visual models suggest that i U. lineatus /i can discriminate both chromatic and achromatic differences in body colouration where longer wavelength light is available. This study demonstrates that i U. lineatus /i have the capacity for colour vision and can likely discriminate colours in the long-wavelength region of the spectrum where the red body pattern reflects light strongly. The ability to see red may therefore provide an advantage in recognising visual signals from conspecifics. This research furthers our understanding of how visual signals have co-evolved with visual abilities, and the role of visual communication in the marine environment.
Sexual dimorphism of the electrosensory system: A quantitative analysis of nerve axons in the dorsal anterior lateral line nerve of the blue-spotted fantail stingray (Taeniura lymma)
Publisher: S. Karger AG
Date: 2013
DOI: 10.1159/000351700
Abstract: Quantitative studies of sensory axons provide invaluable insights into the functional significance and relative importance of a particular sensory modality. Despite the important role electroreception plays in the behaviour of elasmobranchs, to date, there have been no studies that have assessed the number of electrosensory axons that project from the peripheral ullae to the central nervous system (CNS). The complex arrangement and morphology of the peripheral electrosensory system has a significant influence on its function. However, it is not sufficient to base conclusions about function on the peripheral system alone. To fully appreciate the function of the electrosensory system, it is essential to also assess the neural network that connects the peripheral system to the CNS. Using stereological techniques, unbiased estimates of the total number of axons were obtained for both the electrosensory bundles exiting in idual ullary organs and those entering the CNS (via the dorsal root of the anterior lateral line nerve, ALLN) in males and females of different sizes. The dorsal root of the ALLN consists solely of myelinated electrosensory axons and shows both ontogenetic and sexual dimorphism. In particular, females exhibit a greater abundance of electrosensory axons, which may result in improved sensitivity of the electrosensory system and may facilitate mate identification for reproduction. Also presented are detailed morphological data on the peripheral electrosensory system to allow a complete interpretation of the functional significance of the sexual dimorphism found in the ALLN.
Interspecific Visual Adaptations among Wobbegong Sharks (Orectolobidae)
Publisher: S. Karger AG
Date: 2010
DOI: 10.1159/000321330
Abstract: Several visual traits have previously been assessed in elasmobranchs however, few studies have examined and compared multiple visual attributes within a particular genus. The primary advantage of studying closely related species is that any differences between them are more likely to reflect functional ecological adaptations rather than the effects of phylogenetic separation. In this study, the visual capabilities of 4 wobbegong shark species, which vary in life-history and/or habitat, were examined: the western wobbegong i (Orectolobus hutchinsi) /i , the spotted wobbegong i (O /i . i maculatus) /i , the ornate wobbegong i (O /i . i ornatus) /i and the dwarf spotted wobbegong i (O /i . i parvimaculatus) /i . The retinae of all 4 wobbegong species are duplex rod and cone photoreceptors can be distinguished easily on the basis of morphology. Some variation in relative eye size exists, with i O /i . i parvimaculatus /i possessing the largest eyes. The topographic distribution of cells within the ganglion cell layer of i O /i . i hutchinsi /i reveals a weakly elongated central visual streak of increased cell density, mediating a higher spatial resolving power of 2.06 cycles deg sup –1 /sup in the frontal visual field. Retinal topography of i O. maculatus /i and i O. parvimaculatus /i is similar, with both possessing a dorsal horizontal streak facilitating an increased spatial resolving power of 3.51 cycles deg sup –1 /sup and 3.91 cycles deg sup –1 /sup , respectively, in the lower visual field. i O. parvimaculatus /i also possesses an area of increased cell density in the naso-ventral region of the retina, mediating acute vision in the upper caudal region of the visual field. While all 4 species have visual systems optimised for increased visual sensitivity, i O /i . i maculatus /i and i O /i . i arvimaculatus /i appear to be particularly well suited to activity under low light conditions.
A deepwater fish with ‘lightsabers’ – dorsal spine-associated luminescence in a counterilluminating lanternshark
Publisher: Springer Science and Business Media LLC
Date: 21-02-2013
DOI: 10.1038/SREP01308
Cone monochromacy and visual pigment spectral tuning in wobbegong sharks
Publisher: The Royal Society
Date: 19-09-2012
Abstract: Much is known regarding the evolution of colour vision in nearly every vertebrate class, with the notable exception of the elasmobranchs. While multiple spectrally distinct cone types are found in some rays, sharks appear to possess only a single class of cone and, therefore, may be colour blind. In this study, the visual opsin genes of two wobbegong species, Orectolobus maculatus and Orectolobus ornatus , were isolated to verify the molecular basis of their monochromacy. In both species, only two opsin genes are present, RH1 (rod) and LWS (cone), which provide further evidence to support the concept that sharks possess only a single cone type. Examination of the coding sequences revealed substitutions that account for interspecific variation in the photopigment absorbance spectra, which may reflect the difference in visual ecology between these species.
Microspectrophotometric evidence for cone monochromacy in sharks
Publisher: Springer Science and Business Media LLC
Date: 07-01-2011
DOI: 10.1007/S00114-010-0758-8
Abstract: Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks-the rays and chimaeras-are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λ(max) 484-518 nm) and cone (λ(max) 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.
Morphology and spectral absorption characteristics of retinal photoreceptors in the southern hemisphere lamprey (Geotria australis)
Publisher: Cambridge University Press (CUP)
Date: 03-2003
DOI: 10.1017/S0952523803202030
Abstract: The morphology and spectral absorption characteristics of the retinal photoreceptors in the southern hemisphere l rey Geotria australis (Agnatha) were studied using light and electron microscopy and microspectrophotometry. The retinae of both downstream and upstream migrants of Geotria contained two types of cone photoreceptor and one type of rod photoreceptor. Visual pigments contained in the outer segments of these three photoreceptor types had absorbance spectra typical of porphyropsins and with wavelengths of maximum absorbance (downstream/ upstream) at 610/616 nm (long-wavelength-sensitive cone, LWS), 515/515 nm (medium-wavelength-sensitive cone, MWS), and 506/500 nm (medium-wavelength-sensitive rod). A “yellow” photostable pigment was present in the myoid region of all three types of photoreceptor in the downstream migrant. The same short-wavelength-absorbing pigment, which prevents photostimulation of the beta band of the visual pigment in the outer segment, was present in the rods and LWS cones of the upstream migrant, but was replaced by a large transparent ellipsosome in the MWS cones. Using microspectrophotometric and anatomical data, the quantal spectral sensitivity of each photoreceptor type was calculated. Our results provide the first evidence of a jawless vertebrate, represented today solely by the l reys and hagfishes, with two morphologically and physiologically distinct types of cone photoreceptors, in addition to a rod-like photoreceptor containing a colored filter (a cone-like characteristic). In contrast, all other l reys studied thus far have either (1) one type of cone and one type of rod, or (2) a single type of rod-like photoreceptor.
Morphology and distribution of the ampullary electroreceptors in wobbegong sharks: implications for feeding behaviour
Publisher: Springer Science and Business Media LLC
Date: 04-12-2010
Avian colour vision and avian video playback experiments
Publisher: Springer Science and Business Media LLC
Date: 27-05-2020
Ultraviolet Vision in Birds
Publisher: Elsevier
Date: 2000
Visual system evolution and the nature of the ancestral snake
Publisher: Wiley
Date: 16-06-2015
DOI: 10.1111/JEB.12663
Abstract: The dominant hypothesis for the evolutionary origin of snakes from 'lizards' (non-snake squamates) is that stem snakes acquired many snake features while passing through a profound burrowing (fossorial) phase. To investigate this, we examined the visual pigments and their encoding opsin genes in a range of squamate reptiles, focusing on fossorial lizards and snakes. We sequenced opsin transcripts isolated from retinal cDNA and used microspectrophotometry to measure directly the spectral absorbance of the photoreceptor visual pigments in a subset of s les. In snakes, but not lizards, dedicated fossoriality (as in Scolecophidia and the alethinophidian Anilius scytale) corresponds with loss of all visual opsins other than RH1 (λmax 490-497 nm) all other snakes (including less dedicated burrowers) also have functional sws1 and lws opsin genes. In contrast, the retinas of all lizards s led, even highly fossorial hisbaenians with reduced eyes, express functional lws, sws1, sws2 and rh1 genes, and most also express rh2 (i.e. they express all five of the visual opsin genes present in the ancestral vertebrate). Our evidence of visual pigment complements suggests that the visual system of stem snakes was partly reduced, with two (RH2 and SWS2) of the ancestral vertebrate visual pigments being eliminated, but that this did not extend to the extreme additional loss of SWS1 and LWS that subsequently occurred (probably independently) in highly fossorial extant scolecophidians and A. scytale. We therefore consider it unlikely that the ancestral snake was as fossorial as extant scolecophidians, whether or not the latter are para- or monophyletic.
Spatial Resolving Power and Contrast Sensitivity Are Adapted for Ambient Light Conditions in Australian Myrmecia Ants
Publisher: Frontiers Media SA
Date: 12-02-2019
Trichromacy in Australian Marsupials
Publisher: Elsevier BV
Date: 04-2002
DOI: 10.1016/S0960-9822(02)00772-8
Abstract: Vertebrate color vision is best developed in fish, reptiles, and birds with four distinct cone receptor visual pigments. These pigments, providing sensitivity from ultraviolet to infrared light, are thought to have been present in ancestral vertebrates. When placental mammals adopted nocturnality, they lost two visual pigments, reducing them to dichromacy primates subsequently reevolved trichromacy. Studies of mammalian color vision have largely overlooked marsupials despite the wide variety of species and ecological niches and, most importantly, their retention of reptilian retinal features such as oil droplets and double cones. Using microspectrophotometry (MSP), we have investigated the spectral sensitivity of the photoreceptors of two Australian marsupials, the crepuscular, nectivorous honey possum (Tarsipes rostratus) and the arhythmic, insectivorous fat-tailed dunnart (Sminthopsis crassicaudata) these species are representatives of the two major taxonomic isions of marsupials, the diprotodonts and polyprotodonts, respectively. Here, we report the presence of three spectrally distinct cone photoreceptor types in both species. It is the first evidence for the basis of trichromatic color vision in mammals other than primates. We suggest that Australian marsupials have retained an ancestral visual pigment that has been lost from placental mammals.
The effect of underwater sounds on shark behaviour
Publisher: Springer Science and Business Media LLC
Date: 06-05-2019
DOI: 10.1038/S41598-019-43078-W
Abstract: The effect of sound on the behaviour of sharks has not been investigated since the 1970s. Sound is, however, an important sensory stimulus underwater, as it can spread in all directions quickly and propagate further than any other sensory cue. We used a baited underwater camera rig to record the behavioural responses of eight species of sharks (seven reef and coastal shark species and the white shark, Carcharodon carcharias ) to the playback of two distinct sound stimuli in the wild: an orca call sequence and an artificially generated sound. When sounds were playing, reef and coastal sharks were less numerous in the area, were responsible for fewer interactions with the baited test rigs, and displayed less ‘inquisitive’ behaviour, compared to during silent control trials. White sharks spent less time around the baited camera rig when the artificial sound was presented, but showed no significant difference in behaviour in response to orca calls. The use of the presented acoustic stimuli alone is not an effective deterrent for C. carcharias . The behavioural response of reef sharks to sound raises concern about the effects of anthropogenic noise on these taxa.
Dynamic colour change as a signalling tool in bluelined goatfish (Upeneicthtys lineatus)
Publisher: Wiley
Date: 08-2023
DOI: 10.1002/ECE3.10328
Abstract: Many animal species can rapidly change their body colouration and patterning, but often the ecological drivers of such changes are unknown. Here, we explored dynamic colour change in the bluelined goatfish, Upeneichthys lineatus , a temperate marine teleost species. Upeneichthus lineatus can change in a matter of seconds, from a uniform white colour to display prominent, vertical, dark red stripes. Initial observations suggested that rapid colour change in U. lineatus was associated with feeding and may act as a signal to both conspecifics and heterospecifics that are frequently observed to follow feeding goatfish. Field observations of the colour and behaviour of in idual U. lineatus were collected to (1) document the repertoire of behaviours that U. lineatus displays and categorise associated colour patterns (2) quantify the speed of dynamic colour change (3) establish the context in which U. lineatus changes colour and pattern and (4) test whether the behaviour of follower fishes is influenced by colour patterning or specific behaviours of the focal goatfish. We found that U. lineatus changed colouration from white to the red banded pattern in less than 10 s. The key driver of rapid colour change in U. lineatus was feeding, particularly when the fish fed with its head buried in sediment. Conspecific followers were most likely to be white in colour and adopt searching behaviour, regardless of the focal fish colour or behaviour. Other species of follower fish spent significantly more time following U. lineatus that were displaying dark red stripes when searching or eating, implying the red stripes may be an interspecific signalling mechanism. Our findings indicate that rapid colour change in teleost fish may be used for social communication and may provide U. lineatus with increased protection from predation when feeding via a safety‐in‐numbers approach.
Variations in cone photoreceptor abundance and the visual ecology of birds
Publisher: Springer Science and Business Media LLC
Date: 11-2001
DOI: 10.1007/S00359-001-0240-3
Abstract: The relative abundance and topographical distribution of retinal cone photoreceptors was measured in 19 bird species to identify possible correlations between photoreceptor complement and visual ecology. In contrast to previous studies, all five types of cone photoreceptor were distinguished, using bright field and epifluorescent light microscopy, in four retinal quadrants. Land birds tended to show either posterior dorsal to anterior ventral or anterior dorsal to posterior ventral gradients in cone photoreceptor distribution, fundus coloration and oil droplet pigmentation across the retina. Marine birds tended to show dorsal to ventral gradients instead. Statistical analyses showed that the proportions of the different cone types varied significantly across the retinae of all species investigated. Cluster analysis was performed on the data to identify groups or clusters of species on the basis of their oil droplet complement. Using the absolute percentages of each oil droplet type in each quadrant for the analysis produced clusters that tended to reflect phylogenetic relatedness between species rather than similarities in their visual ecology. Repeating the analysis after subtracting the mean percentage of a given oil droplet type across the whole retina (the 'eye mean') from the percentage of that oil droplet type in each quadrant, i.e. to give a measure of the variation about the mean, resulted in clusters that reflected diet, feeding behaviour and habitat to a greater extent than phylogeny.
Spectral sensitivities of the seahorsesHippocampus subelongatusandHippocampus barbouriand the pipefishStigmatopora argus
Publisher: Cambridge University Press (CUP)
Date: 05-2007
DOI: 10.1017/S0952523807070320
Abstract: The Syngnathidae are specialized diurnal feeders that are known to possess a retinal fovea and use independent eye movements to locate, track, and strike in idual planktonic prey items. In this study, we have investigated the spectral sensitivities of three syngnathid species: a pipefish and two seahorses. We used spectrophotometry to measure the spectral transmission properties of ocular lenses and microspectrophotometry to measure the spectral absorption characteristics of visual pigments in the retinal photoreceptors. The pipefish, Stigmatopora argus , together with the seahorse Hippoc us subelongatus , is found in “green-water” temperate coastal seagrass habitats, whereas the second seahorse, H. barbouri , originates from a “blue-water” tropical coral reef habitat. All species were found to possess short wavelength absorbing pigment(s) in their lenses, with the 50% cut-off point of S. argus and H. subelongatus at 429 and 425 nm respectively, whereas that of H. barbouri was located at 409 nm. Microspectrophotometry of the photoreceptors revealed that the rods of all three species contained visual pigment with the wavelength of maximum absorption (λ max ) at approximately 500 nm. The visual pigment complement of the cones varied between the species: all possessed single cones with a λ max close to 460 nm but H. barbouri also possessed an additional class of single cone with λ max at 430 nm. Three classes of visual pigment were found in the double cones, the λ max being approximately 520, 537, and 560 nm in the two seahorses and 520, 537, and 580 nm in the pipefish. The spectral sensitivities of the syngnathids investigated here do not appear to conform to generally accepted trends for fishes inhabiting different spectral environments. The influence of the specialized feeding regime of the syngnathids is discussed in relation to our findings that ultra-violet sensitivity is apparently not necessary for zooplanktivory in certain habitats.
Red/near-infrared irradiation therapy for treatment of central nervous system injuries and disorders.
Publisher: Walter de Gruyter GmbH
Date: 2013
Prey interactions in tiger sharks: Accounting for visual perception in animal-borne cameras
Publisher: Elsevier BV
Date: 08-2022
Spectral Diversification and Trans-Species Allelic Polymorphism during the Land-to-Sea Transition in Snakes
Publisher: Elsevier BV
Date: 07-2020
Retinal Characteristics of the Ornate Dragon Lizard, Ctenophorus ornatus
Publisher: Wiley
Date: 25-07-2002
DOI: 10.1002/CNE.10308
Abstract: The retina of a diurnal insectivorous lizard, Ctenophorus ornatus (Agamidae) was investigated using microspectrophotometry and light and electron microscopy. A prominent broad yellow band was observed that extended across the mid-retina. The yellow coloration was found to originate from both oil droplets and diffuse pigmentation within cone inner segments. Microspectrophotometric analysis revealed yellow oil droplets with variable absorption of wavelengths below 520 nm and transparent oil droplets with no detectable absorptance between 350 and 750 nm. Cones with transparent oil droplets lacked the diffuse yellow pigmentation. The mean wavelengths of maximum absorbance of visual pigments in the isolated cone outer segments were at 440, 493, and 571 nm. The retina was found to possess a deep convexiclivate fovea located within the yellow band, slightly dorsotemporal of the retinal midpoint. The topography of the retinal ganglion cells revealed that the fovea was contained within an area centralis. Photoreceptors were either single (80%) or unequal double (20%) cones. Within the region of the fovea, the cones were approximately 20% the diameter of those in the peripheral retina. Colored oil droplets and yellow pigment may increase visual acuity by absorbing short wavelength light scattered either by the atmosphere or the optical structures of the eye. The presence of a fovea containing slender cone photoreceptors and three visual pigments suggests that the lizard has high acuity and the potential for color vision.
Visual Opsin Diversity in Sharks and Rays
Publisher: Oxford University Press (OUP)
Date: 26-11-2019
Abstract: The ersity of color vision systems found in extant vertebrates suggests that different evolutionary selection pressures have driven specializations in photoreceptor complement and visual pigment spectral tuning appropriate for an animal’s behavior, habitat, and life history. Aquatic vertebrates in particular show high variability in chromatic vision and have become important models for understanding the role of color vision in prey detection, predator avoidance, and social interactions. In this study, we examined the capacity for chromatic vision in elasmobranch fishes, a group that have received relatively little attention to date. We used microspectrophotometry to measure the spectral absorbance of the visual pigments in the outer segments of in idual photoreceptors from several ray and shark species, and we sequenced the opsin mRNAs obtained from the retinas of the same species, as well as from additional elasmobranch species. We reveal the phylogenetically widespread occurrence of dichromatic color vision in rays based on two cone opsins, RH2 and LWS. We also confirm that all shark species studied to date appear to be cone monochromats but report that in different species the single cone opsin may be of either the LWS or the RH2 class. From this, we infer that cone monochromacy in sharks has evolved independently on multiple occasions. Together with earlier discoveries in secondarily aquatic marine mammals, this suggests that cone-based color vision may be of little use for large marine predators, such as sharks, pinnipeds, and cetaceans.
Colour vision and visual ecology of the blue-spotted maskray, Dasyatis kuhlii Müller & Henle, 1814
Publisher: Springer Science and Business Media LLC
Date: 26-09-2007
DOI: 10.1007/S00359-006-0171-0
Abstract: Relatively little is known about the physical structure and ecological adaptations of elasmobranch sensory systems. In particular, elasmobranch vision has been poorly studied compared to the other senses. Virtually nothing is known about whether elasmobranchs possess multiple cone types, and therefore the potential for colour vision, or how the spectral tuning of their visual pigments is adapted to their different lifestyles. In this study, we measured the spectral absorption of the rod and cone visual pigments of the blue-spotted maskray, Dasyatis kuhlii, using microspectrophotometry. D. kuhlii possesses a rod visual pigment with a wavelength of maximum absorbance (lambda(max)) at 497 nm and three spectrally distinct cone types with lambda(max) values at 476, 498 and 552 nm. Measurements of the spectral transmittance of the ocular media reveal that wavelengths below 380 nm do not reach the retina, indicating that D. kuhlii is relatively insensitive to ultraviolet radiation. Topographic analysis of retinal ganglion cell distribution reveals an area of increased neuronal density in the dorsal retina. Based on peak cell densities and using measurements of lens focal length made using laser ray tracing and sections of frozen eyes, the estimated spatial resolving power of D. kuhlii is 4.10 cycles per degree.
Visual opsin expression and morphological characterization of retinal photoreceptors in the pouched lamprey (
Geotria australis
,
Publisher: Wiley
Date: 30-12-2020
DOI: 10.1002/CNE.25092
Abstract: L reys are extant members of the agnathan (jawless) vertebrates that erged ~500 million years ago, during a critical stage of vertebrate evolution when image-forming eyes first emerged. Among l rey species assessed thus far, the retina of the southern hemisphere pouched l rey, Geotria australis, is unique, in that it possesses morphologically distinct photoreceptors and expresses five visual photopigments. This study focused on determining the number of different photoreceptors present in the retina of G. australis and whether each cell type expresses a single opsin class. Five photoreceptor subtypes were identified based on ultrastructure and differential expression of one of each of the five different visual opsin classes (lws, sws1, sws2, rh1, and rh2) known to be expressed in the retina. This suggests, therefore, that the retina of G. australis possesses five spectrally and morphologically distinct photoreceptors, with the potential for complex color vision. Each photoreceptor subtype was shown to have a specific spatial distribution in the retina, which is potentially associated with changes in spectral radiance across different lines of sight. These results suggest that there have been strong selection pressures for G. australis to maintain broad spectral sensitivity for the brightly lit surface waters that this species inhabits during its marine phase. These findings provide important insights into the functional anatomy of the early vertebrate retina and the selection pressures that may have led to the evolution of complex color vision.
Visual pigments, cone oil droplets, ocular media and predicted spectral sensitivity in the domestic turkey (Meleagris gallopavo)
Publisher: Elsevier BV
Date: 10-1999
DOI: 10.1016/S0042-6989(99)00071-1
Abstract: A microspectrophotometric survey conducted on the retinal photoreceptors of the domestic turkey (Meleagris gallopavo) revealed the presence of five different types of vitamin A1-based visual pigment (rhodopsin) in seven different types of photoreceptor. A single class of rod contained a medium wavelength-sensitive visual pigment (wavelength of maximum absorbance, lambda max, 504 nm). Four different types of single cone contained visual pigment maximally sensitive to wavelengths in either the long (LWS, lambda max 564 nm), medium (MWS, lambda max 505 nm), short (SWS, lambda max 460 nm) or violet (VS, lambda max 420 nm) spectral ranges. The LWS, MWS and SWS single cones contained pigmented oil droplets with cut-off wavelengths (lambda cut) at 514, 490 and 437 nm, respectively. The VS single cone contained a transparent oil droplet which displayed no significant absorbance above 330 nm. A single class of double cone was also identified, both the principal and accessory members of which contained the LWS cone visual pigment. The principal member contained an oil droplet with a lambda cut at 436 nm. No oil droplet was observed in the accessory member. The use of a glycerol-based cell mountant, which reduced wavelength dependent measurement artefacts in the microspectrophotometric measurements, is described. Predictions of cone effective spectral sensitivity, incorporating measurements of the spectral transmission of the ocular media, suggest that turkeys have considerable sensitivity to wavelengths in the ultraviolet-A (UV-A, 315-400 nm) spectral range. This has implications for both the visual ecology of wild birds and the welfare of intensively farmed in iduals.
The mechanosensory lateral line system in two species of wobbegong shark (Orectolobidae)
Publisher: Springer Science and Business Media LLC
Date: 07-06-2012
Spectral Tuning in the Eyes of Deep-Sea Lanternfishes (Myctophidae): A Novel Sexually Dimorphic Intra-Ocular Filter
Publisher: S. Karger AG
Date: 2015
DOI: 10.1159/000371652
Abstract: Deep-sea fishes possess several adaptations to facilitate vision where light detection is pushed to its limit. Lanternfishes (Myctophidae), one of the world's most abundant groups of mesopelagic fishes, possess a novel and unique visual specialisation, a sexually dimorphic photostable yellow pigmentation, constituting the first record of a visual sexual dimorphism in any non-primate vertebrate. The topographic distribution of the yellow pigmentation across the retina is species specific, varying in location, shape and size. Spectrophotometric analyses reveal that this new retinal specialisation differs between species in terms of composition and acts as a filter, absorbing maximally between 356 and 443 nm. Microspectrophotometry and molecular analyses indicate that the species containing this pigmentation also possess at least 2 spectrally distinct rod visual pigments as a result of a duplication of the i Rh1 /i opsin gene. After modelling the effect of the yellow pigmentation on photoreceptor spectral sensitivity, we suggest that this unique specialisation acts as a filter to enhance contrast, thereby improving the detection of bioluminescent emissions and possibly fluorescence in the extreme environment of the deep sea. The fact that this yellow pigmentation is species specific, sexually dimorphic and isolated within specific parts of the retina indicates an evolutionary pressure to visualise prey redators/mates in a particular part of each species' visual field.
Electrosensory-driven feeding behaviours of the Port Jackson shark (Heterodontus portusjacksoni) and western shovelnose ray (Aptychotrema vincentiana)
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/MF14245
Abstract: Elasmobranch fishes (sharks, skates and rays) possess a highly sensitive electrosensory system that enables them to detect weak electric fields, such as those produced by potential prey organisms. Despite several comparative anatomical studies, the functional significance of interspecific variation in electrosensory system morphology remains poorly understood. In the present study, we directly tested the electrosensitivity of two benthic elasmobranchs that share a similar habitat and feed on similarly sized prey items (Port Jackson sharks, Heterodontus portusjacksoni, and western shovelnose rays, Aptychotrema vincentiana), but differ significantly in their electrosensory system morphology. Aptychotrema vincentiana possesses almost five times the number of electrosensory pores of H. portusjacksoni (~1190 and ~239 respectively), yet both species are able to initiate feeding responses to electric-field gradients below 1 nV cm–1, similar to other elasmobranch species tested. However, A. vincentiana showed a greater ability to resolve the specific location of electrosensory stimuli, because H. portusjacksoni would more often overshoot the target and have to turn around to locate it. These results suggested that differences in abundance and distribution of electrosensory pores have little to no effect on the absolute electrical sensitivity in elasmobranchs, and instead, may reflect species-specific differences in the spatial resolution and directionality of electroreception.
Retinal Ganglion Cell Topography and Spatial Resolving Power in Penguins
Publisher: S. Karger AG
Date: 2012
DOI: 10.1159/000341901
Abstract: Penguins are a group of flightless seabirds that exhibit numerous morphological, behavioral and ecological adaptations to their hibious lifestyle, but little is known about the topographic organization of neurons in their retinas. In this study, we used retinal wholemounts and stereological methods to estimate the total number and topographic distribution of retinal ganglion cells in addition to an anatomical estimate of spatial resolving power in two species of penguins: the little penguin, i Eudyptula minor, /i and the king penguin, i Aptenodytes patagonicus. /i The total number of ganglion cells per retina was approximately 1,200,000 in the little penguin and 1,110,000 in the king penguin. The topographic distribution of retinal ganglion cells in both species revealed the presence of a prominent horizontal visual streak with steeper gradients in the little penguin. The little penguin retinas showed ganglion cell density peaks of 21,867 cells/mm sup /sup , affording spatial resolution in water of 17.07–17.46 cycles/degree (12.81–13.09 cycles/degree in air). In contrast, the king penguin showed a relatively lower peak density of ganglion cells of 14,222 cells/mm sup /sup , but – due to its larger eye – slightly higher spatial resolution in water of 20.40 cycles/degree (15.30 cycles/degree in air). In addition, we mapped the distribution of giant ganglion cells in both penguin species using Nissl-stained wholemounts. In both species, topographic mapping of this cell type revealed the presence of an area gigantocellularis with a concentric organization of isodensity contours showing a peak in the far temporal retina of approximately 70 cells/mm sup /sup in the little penguin and 39 cells/mm sup /sup in the king penguin. Giant ganglion cell densities gradually fall towards the outermost isodensity contours revealing the presence of a vertically organized streak. In the little penguin, we confirmed our cytological characterization of giant ganglion cells using immunohistochemistry for microtubule-associated protein 2. This suite of retinal specializations, which is also observed in the closely related procellariiform seabirds, affords the eyes of the little and king penguins panoramic surveillance of the horizon and motion detection in the frontal visual field.
Retinal neurogenesis and ontogenetic changes in the visual system of the brown banded bamboo shark,Chiloscyllium punctatum(hemiscyllidae, elasmobranchii)
Publisher: Wiley
Date: 03-2009
DOI: 10.1002/CNE.21953
Abstract: The development of the eye of the oviparous brown banded bamboo shark, Chiloscyllium punctatum, was monitored from egg deposition through adulthood. The order and timing of retinal cell differentiation were assessed by light and transmission electron microscopy. As in other vertebrates, the ganglion cells are the first to differentiate, in this case by 81 days post-egg deposition (dpd). The order then deviates from what is typically quoted for vertebrates, with the Müller and amacrine cells differentiating morphologically around the same time, followed by the bipolar cells (101 dpd) and finally the horizontal cells and photoreceptors (124 dpd). The neural retina is fully differentiated and synaptic connections are formed approximately 1 month prior to hatching, which occurs at about 158 dpd. The mature retina is duplex, with a peak rod to cone ratio of approximately 12:1. The eye and lens of C. punctatum continue to grow throughout life and become less aspherical with growth the equatorial (nasotemporal) lens diameter is 12% larger than the axial (anterior-posterior) lens diameter in embryos and 8% larger in adults. Access to developmental stages and the protracted gestational period of C. punctatum make it a highly valuable model for developmental studies of the visual system. This study also provides an evolutionary perspective on retinal neurogenesis in an elasmobranch.
Ocellar spatial vision in Myrmecia ants
Publisher: The Company of Biologists
Date: 15-10-2021
DOI: 10.1242/JEB.242948
Abstract: In addition to compound eyes, insects possess simple eyes known as ocelli. Input from the ocelli modulates optomotor responses, flight-time initiation, and phototactic responses – behaviours that are mediated predominantly by the compound eyes. In this study, using pattern electroretinography (pERG), we investigated the contribution of the compound eyes to ocellar spatial vision in the diurnal Australian bull ant Myrmecia tarsata by measuring the contrast sensitivity and spatial resolving power of the ocellar second-order neurons under various occlusion conditions. Furthermore, in four species of Myrmecia ants active at different times of the day, and in European honeybee Apis mellifera, we characterized the ocellar visual properties when both visual systems were available. Among the ants, we found that the time of activity had no significant effect on ocellar spatial vision. Comparing day-active ants and the honeybee, we did not find any significant effect of locomotion on ocellar spatial vision. In M. tarsata, when the compound eyes were occluded, the litude of the pERG signal from the ocelli was reduced 3 times compared with conditions when the compound eyes were available. The signal from the compound eyes maintained the maximum contrast sensitivity of the ocelli as 13 (7.7%), and the spatial resolving power as 0.29 cycles deg−1. We conclude that ocellar spatial vison improves significantly with input from the compound eyes, with a noticeably larger improvement in contrast sensitivity than in spatial resolving power.
A comparison of spatial analysis methods for the construction of topographic maps of retinal cell density
Publisher: Public Library of Science (PLoS)
Date: 18-04-2014
How Close is too Close? The Effect of a Non-Lethal Electric Shark Deterrent on White Shark Behaviour
Publisher: Public Library of Science (PLoS)
Date: 07-2016
Fluorescence characterisation and visual ecology of pseudocheilinid wrasses
Publisher: Springer Science and Business Media LLC
Date: 15-03-2016
Vision in elasmobranchs and their relatives: 21st century advances
Publisher: Wiley
Date: 22-03-2012
DOI: 10.1111/J.1095-8649.2012.03253.X
Abstract: This review identifies a number of exciting new developments in the understanding of vision in cartilaginous fishes that have been made since the turn of the century. These include the results of studies on various aspects of the visual system including eye size, visual fields, eye design and the optical system, retinal topography and spatial resolving power, visual pigments, spectral sensitivity and the potential for colour vision. A number of these studies have covered a broad range of species, thereby providing valuable information on how the visual systems of these fishes are adapted to different environmental conditions. For ex le, oceanic and deep-sea sharks have the largest eyes amongst elasmobranchs and presumably rely more heavily on vision than coastal and benthic species, while interspecific variation in the ratio of rod and cone photoreceptors, the topographic distribution of the photoreceptors and retinal ganglion cells in the retina and the spatial resolving power of the eye all appear to be closely related to differences in habitat and lifestyle. Multiple, spectrally distinct cone photoreceptor visual pigments have been found in some batoid species, raising the possibility that at least some elasmobranchs are capable of seeing colour, and there is some evidence that multiple cone visual pigments may also be present in holocephalans. In contrast, sharks appear to have only one cone visual pigment. There is evidence that ontogenetic changes in the visual system, such as changes in the spectral transmission properties of the lens, lens shape, focal ratio, visual pigments and spatial resolving power, allow elasmobranchs to adapt to environmental changes imposed by habitat shifts and niche expansion. There are, however, many aspects of vision in these fishes that are not well understood, particularly in the holocephalans. Therefore, this review also serves to highlight and stimulate new research in areas that still require significant attention.
Visual pigments, ocular filters and the evolution of snake vision
Publisher: Oxford University Press (OUP)
Date: 16-08-2016
Abstract: Much of what is known about the molecular evolution of vertebrate vision comes from studies of mammals, birds and fish. Reptiles (especially snakes) have barely been s led in previous studies despite their exceptional ersity of retinal photoreceptor complements. Here, we analyze opsin gene sequences and ocular media transmission for up to 69 species to investigate snake visual evolution. Most snakes express three visual opsin genes (rh1, sws1, and lws). These opsin genes (especially rh1 and sws1) have undergone much evolutionary change, including modifications of amino acid residues at sites of known importance for spectral tuning, with several tuning site combinations unknown elsewhere among vertebrates. These changes are particularly common among dipsadine and colubrine "higher" snakes. All three opsin genes are inferred to be under purifying selection, though dN/dS varies with respect to some lineages, ecologies, and retinal anatomy. Positive selection was inferred at multiple sites in all three opsins, these being concentrated in transmembrane domains and thus likely to have a substantial effect on spectral tuning and other aspects of opsin function. Snake lenses vary substantially in their spectral transmission. Snakes active at night and some of those active by day have very transmissive lenses, whereas some primarily diurnal species cut out shorter wavelengths (including UVA). In terms of retinal anatomy, lens transmission, visual pigment spectral tuning and opsin gene evolution the visual system of snakes is exceptionally erse compared with all other extant tetrapod orders.
Physiological properties of the visual system in the Green Weaver ant, Oecophylla smaragdina
Publisher: Springer Science and Business Media LLC
Date: 13-04-2023
DOI: 10.1007/S00359-023-01629-7
Abstract: The Green Weaver ants, Oecophylla smaragdina are iconic animals known for their extreme cooperative behaviour where they bridge gaps by linking to each other to build living chains. They are visually oriented animals, build chains towards closer targets, use celestial compass cues for navigation and are visual predators. Here, we describe their visual sensory capacity. The major workers of O. smaragdina have more ommatidia (804) in each eye compared to minor workers (508), but the facet diameters are comparable between both castes. We measured the impulse responses of the compound eye and found their response duration (42 ms) was similar to that seen in other slow-moving ants. We determined the flicker fusion frequency of the compound eye at the brightest light intensity to be 132 Hz, which is relatively fast for a walking insect suggesting the visual system is well suited for a diurnal lifestyle. Using pattern-electroretinography we identified the compound eye has a spatial resolving power of 0.5 cycles deg −1 and reached peak contrast sensitivity of 2.9 (35% Michelson contrast threshold) at 0.05 cycles deg −1 . We discuss the relationship of spatial resolution and contrast sensitivity, with number of ommatidia and size of the lens.
Morphology, Characterization and Distribution of Retinal Photoreceptors in the South American (Lepidosiren paradoxa) and Spotted African (Protopterus dolloi) Lungfishes
Publisher: Frontiers Media SA
Date: 24-06-2016
The evolution of early vertebrate photoreceptors
Publisher: The Royal Society
Date: 12-10-2009
Abstract: Meeting the challenge of s ling an ancient aquatic landscape by the early vertebrates was crucial to their survival and would establish a retinal bauplan to be used by all subsequent vertebrate descendents. Image-forming eyes were under tremendous selection pressure and the ability to identify suitable prey and detect potential predators was thought to be one of the major drivers of speciation in the Early Cambrian. Based on the fossil record, we know that hagfishes, l reys, holocephalans, elasmobranchs and lungfishes occupy critical stages in vertebrate evolution, having remained relatively unchanged over hundreds of millions of years. Now using extant representatives of these ‘living fossils’, we are able to piece together the evolution of vertebrate photoreception. While photoreception in hagfishes appears to be based on light detection and controlling circadian rhythms, rather than image formation, the photoreceptors of l reys fall into five distinct classes and represent a critical stage in the dichotomy of rods and cones. At least four types of retinal cones s le the visual environment in l reys mediating photopic (and potentially colour) vision, a s ling strategy retained by lungfishes, some modern teleosts, reptiles and birds. Trichromacy is retained in cartilaginous fishes (at least in batoids and holocephalans), where it is predicted that true scotopic (dim light) vision evolved in the common ancestor of all living gnathostomes. The capacity to discriminate colour and balance the tradeoff between resolution and sensitivity in the early vertebrates was an important driver of eye evolution, where many of the ocular features evolved were retained as vertebrates progressed on to land.
Optimal preservation of the shark retina for ultrastructural analysis: An assessment of chemical, microwave, and high‐pressure freezing fixation techniques
Publisher: Wiley
Date: 12-05-2012
DOI: 10.1002/JEMT.22052
Abstract: Recent advances in microwave chemical fixation (MCF) and/or high pressure freezing (HPF) combined with transmission electron microscopy have resulted in superior ultrastructural detail in a variety of tissue types. To date, selachian tissue has been fixed and processed using only standard chemical fixation (CF) methods, and the resulting ultrastructure has been less than ideal. In this study, we compared the ultrastructure of the fragile retinal tissue from the brown banded bamboo shark, Chiloscyllium punctatum, obtained using CF, MCF, and HPF methods. For all fixation protocols, ultrastructural preservation was improved by keeping the tissue in oxygenated Ringer solution until the time of fixation. Both MCF and HPF produced superior retinal ultrastructure compared to conventional CF. Although HPF occasionally resulted in very high quality ultrastructure, microwave fixation was almost comparable, quicker and far more consistent.
Limited variation in visual sensitivity among bowerbird species suggests that there is no link between spectral tuning and variation in display colouration
Publisher: The Company of Biologists
Date: 04-2012
DOI: 10.1242/JEB.062224
Abstract: Variation in visual spectral tuning has evolved in concert with signal colour in some taxa, but there is limited evidence of this pattern in birds. To further investigate this possibility, we compared spectral sensitivity among bowerbird species that occupy different visual habitats and are highly erged in plumage and decoration colour displays, which are important in mate choice and possibly reproductive isolation. Microspectrophotometry of violet-, short-, medium- and long-wavelength-sensitive cones revealed no significant interspecific variation in visual pigment peak spectral absorbance values that ranged between 404–410, 454, 503–511 and 558–568 nm, respectively. Mean cut-off wavelength values for C-, Y-, R- and P-type coloured oil droplets were 418–441, 508–523, 558–573 and 412–503 nm, respectively, with values at longer wavelengths in ventral compared with dorsal retina cones. Low ocular media mid-wavelength transmission values (340–352 nm) suggest that bowerbirds may represent a transitional stage in the evolution from the ancestral violet-sensitive- to the derived ultraviolet-sensitive-type short-wavelength-sensitive-1-based visual system found in younger passerine lineages. Sequence data obtained for rod opsin and four cone opsin genes were identical at key tuning sites, except for an interspecific leucine-52-alanine polymorphism in the short-wavelength-sensitive 2 opsin. There was no obvious relationship between relative proportions of cone classes and either visual habitat or display colour. Overall, we detected little interspecific variation in bowerbird spectral sensitivity and no association between sensitivity and display ersity, which is consistent with the general trend among avian taxa.
Regional distribution of nitrergic neurons in the inner retina of the chicken
Publisher: Cambridge University Press (CUP)
Date: 19-04-2011
DOI: 10.1017/S0952523811000083
Abstract: Using both NADPH diaphorase and anti-nNOS antibodies, we have identified—from retinal flatmounts—neuronal types in the inner retina of the chicken that are likely to be nitrergic. The two methods gave similar results and yielded a total of 15 types of neurons, comprising 9 amacrine cells, 5 ganglion cells, and 1 centrifugal midbrain neuron. Six of these 15 cell types are ubiquitously distributed, comprising 3 amacrine cells, 2 displaced ganglion cells, and a presumed orthotopic ganglion cell. The remaining nine cell types are regionally restricted within the retina. As previously reported, efferent fibers of midbrain neurons and their postsynaptic partners, the unusual axon-bearing target amacrine cells, are entirely confined to the ventral retina. Also confined to the ventral retina, though with somewhat different distributions, are the “bullwhip” amacrine cells thought to be involved in eye growth, an orthotopic ganglion cell, and two types of large axon-bearing amacrine cells whose dendrites and axons lie in stratum 1 of the inner plexiform layer (IPL). Intracellular fills of these two cell types showed that only a minority of otherwise morphologically indistinguishable neurons are nitrergic. Two amacrine cells that branch throughout the IPL are confined to an equatorial band, and one small-field orthotopic ganglion cell that branches in the proximal IPL is entirely dorsal. These findings suggest that the retina uses different processing on different regions of the visual image, though the benefit of this is presently obscure.
Ancestral duplications and highly dynamic opsin gene evolution in percomorph fishes
Publisher: Proceedings of the National Academy of Sciences
Date: 29-12-2014
Abstract: Gene and whole-genome duplications are important evolutionary forces promoting organismal ersification. Teleost fishes, for ex le, possess many gene duplicates responsible for photoreception (opsins), which emerged through gene duplication and allow fishes to adapt to the various light conditions of the aquatic environment. Here, we reevaluate the evolutionary history of the violet-blue–sensitive opsins [short wavelength-sensitive 2 (SWS2)] in modern teleosts using next generation genome sequencing. We uncover a gene duplication event specific to the most erse lineage of vertebrates (the percomorphs) and show that SWS2 evolution was highly dynamic and involved gene loss, pseudogenization, and gene conversion. We, thus, clarify previous discrepancies regarding opsin annotations. Our study highlights the importance of integrative approaches to help us understand how species adapt and ersify.
Ontogenetic shifts in brain scaling reflect behavioral changes in the life cycle of the pouched lamprey Geotria australis
Publisher: Frontiers Media SA
Date: 28-07-2015
Vision in the southern hemisphere lampreyMordacia mordax: Spatial distribution, spectral absorption characteristics, and optical sensitivity of a single class of retinal photoreceptor
Publisher: Cambridge University Press (CUP)
Date: 09-2004
DOI: 10.1017/S0952523804215103
Abstract: The dorso-laterally located eyes of the southern hemisphere l rey Mordacia mordax (Agnatha) contain a single morphological type of retinal photoreceptor, which possesses ultrastructural characteristics of both rods and cones. This photoreceptor has a large refractile ellipsosome in the inner segment and a long cylindrical outer segment surrounded by a retinal pigment epithelium that contains two types of tapetal reflectors. The photoreceptors form a hexagonal array and attain their peak density (33,200 receptors/mm 2 ) in the ventro-temporal retina. Using the size and spacing of the photoreceptors and direct measures of aperture size and eye dimensions, the peak spatial resolving power and optical sensitivity are estimated to be 1.7 cycles deg −1 (minimum separable angle of 34′7′′) and 0.64 μm 2 steradian (white light) and 1.38 μm 2 steradian (preferred wavelength or λ max ), respectively. Microspectrophotometry reveals that the visual pigment located within the outer segment is a rhodopsin with a wavelength of maximum absorbance (λ max ) at 514 nm. The ellipsosome has very low absorptance ( .05) across the measured spectrum (350–750 nm) and probably does not act as a spectral filter. In contrast to all other l reys studied, the optimized receptor packing, the large width of the ellipsosome-bearing inner segment, together with the presence of a retinal tapetum in the photophobic Mordacia , all represent adaptations for low light vision and optimizing photon capture.
Sexual selection based on egg colour: physiological models and egg discrimination experiments in a cavity-nesting bird
Publisher: Springer Science and Business Media LLC
Date: 21-04-2011
An Integrative Framework for the Appraisal of Coloration in Nature
Publisher: University of Chicago Press
Date: 06-2015
DOI: 10.1086/681021
Abstract: The world in color presents a dazzling dimension of phenotypic variation. Biological interest in this variation has burgeoned, due to both increased means for quantifying spectral information and heightened appreciation for how animals view the world differently than humans. Effective study of color traits is challenged by how to best quantify visual perception in nonhuman species. This requires consideration of at least visual physiology but ultimately also the neural processes underlying perception. Our knowledge of color perception is founded largely on the principles gained from human psychophysics that have proven generalizable based on comparative studies in select animal models. Appreciation of these principles, their empirical foundation, and the reasonable limits to their applicability is crucial to reaching informed conclusions in color research. In this article, we seek a common intellectual basis for the study of color in nature. We first discuss the key perceptual principles, namely, retinal photoreception, sensory channels, opponent processing, color constancy, and receptor noise. We then draw on this basis to inform an analytical framework driven by the research question in relation to identifiable viewers and visual tasks of interest. Consideration of the limits to perceptual inference guides two primary decisions: first, whether a sensory-based approach is necessary and justified and, second, whether the visual task refers to perceptual distance or discriminability. We outline informed approaches in each situation and discuss key challenges for future progress, focusing particularly on how animals perceive color. Given that animal behavior serves as both the basic unit of psychophysics and the ultimate driver of color ecology/evolution, behavioral data are critical to reconciling knowledge across the schools of color research.
Effects of auditory and visual stimuli on shark feeding behaviour: the disco effect
Publisher: Springer Science and Business Media LLC
Date: 13-11-2017
Cone photoreceptor oil droplet pigmentation is affected by ambient light intensity
Publisher: The Company of Biologists
Date: 12-2006
DOI: 10.1242/JEB.02568
Abstract: The cone photoreceptors of many vertebrates contain spherical organelles called oil droplets. In birds, turtles, lizards and some lungfish the oil droplets are heavily pigmented and function to filter the spectrum of light incident upon the visual pigment within the outer segment. Pigmented oil droplets are beneficial for colour discrimination in bright light, but at lower light levels the reduction in sensitivity caused by the pigmentation increasingly outweighs the benefits generated by spectral tuning. Consequently, it is expected that species with pigmented oil droplets should modulate the density of pigment in response to ambient light intensity and thereby regulate the amount of light transmitted to the outer segment. In this study, microspectrophotometry was used to measure the absorption spectra of cone oil droplets in chickens (Gallus gallus domesticus) reared under bright (unfiltered) or dim (filtered) sunlight. Oil droplet pigmentation was found to be dependent on the intensity of the ambient light and the duration of exposure to the different lighting treatments. In adult chickens reared in bright light, the oil droplets of all cone types (except the violet-sensitive single cones, whose oil droplet is always non-pigmented) were more densely pigmented than those in chickens reared in dim light. Calculations show that the reduced levels of oil droplet pigmentation in chickens reared in dim light would increase the sensitivity and spectral bandwidth of the outer segment significantly. The density of pigmentation in the oil droplets presumably represents a trade-off between the need for good colour discrimination and absolute sensitivity. This might also explain why nocturnal animals, or those that underwent a nocturnal phase during their evolution, have evolved oil droplets with low pigment densities or no pigmentation or have lost their oil droplets altogether.
Spatial resolving power and spectral sensitivity of the saltwater crocodile, Crocodylus porosus, and the freshwater crocodile, Crocodylus johnstoni
Publisher: The Company of Biologists
Date: 05-2016
DOI: 10.1242/JEB.135673
Abstract: Crocodilians are apex hibious predators that occupy a range of tropical habitats. In this study, we examined whether their semi-aquatic lifestyle and ambush hunting mode are reflected in specific adaptations in the peripheral visual system. Design-based stereology and microspectrophotometry were used to assess spatial resolving power and spectral sensitivity of saltwater (Crocodylus porosus) and freshwater crocodiles (Crocodylus johnstoni). Both species possess a foveal streak that spans the naso-temporal axis and mediates high spatial acuity across the central visual field. The saltwater crocodile and freshwater crocodile have a peak spatial resolving power of 8.8 and 8.0 cycles deg−1, respectively. Measurement of the outer segment dimensions and spectral absorbance revealed five distinct photoreceptor types consisting of three single cones, one twin cone and a rod. The three single cones (saltwater/freshwater crocodile) are violet (424/426 nm λmax), green (502/510 nm λmax) and red (546/554 nm λmax) sensitive, indicating the potential for trichromatic colour vision. The visual pigments of both members of the twin cones have the same λmax as the red-sensitive single cone and the rod has a λmax at 503/510 nm (saltwater/freshwater). The λmax values of all types of visual pigment occur at longer wavelengths in the freshwater crocodile compared with the saltwater crocodile. Given that there is a greater abundance of long wavelength light in freshwater compared with a saltwater environment, the photoreceptors would be more effective at detecting light in their respective habitats. This suggests that the visual systems of both species are adapted to the photic conditions of their respective ecological niche.
Tank color increases growth, and alters color preference and spectral sensitivity, in barramundi (Lates calcarifer)
Publisher: Elsevier BV
Date: 12-2011
The phylogeny of halichondrid demosponges: past and present re-visited with DNA-barcoding data
Publisher: Springer Science and Business Media LLC
Date: 03-2012
Enhanced short-wavelength sensitivity in the blue-tongued skink Tiliqua rugosa
Publisher: The Company of Biologists
Date: 06-2022
DOI: 10.1242/JEB.244317
Abstract: Despite lizards using a wide range of colour signals, the limited variation in photoreceptor spectral sensitivities across lizards suggests only weak selection for species-specific, spectral tuning of photoreceptors. Some species, however, have enhanced short-wavelength sensitivity, which probably helps with the detection of signals rich in ultraviolet and short wavelengths. In this study, we examined the visual system of Tiliqua rugosa, which has an ultraviolet/blue tongue, to gain insight into this species' visual ecology. We used electroretinograms, opsin sequencing and immunohistochemical labelling to characterize whole-eye spectral sensitivity and the elements that shape it. Our findings reveal that T. rugosa expresses all five opsins typically found in lizards (SWS1, SWS2, RH1, RH2 and LWS) but possesses greatly enhanced short-wavelength sensitivity compared with other diurnal lizards. This enhanced short-wavelength sensitivity is characterized by a broadening of the spectral sensitivity curve of the eye towards shorter wavelengths while the peak sensitivity of the eye at longer wavelengths (560 nm) remains similar to that of other diurnal lizards. While an increased abundance of SWS1 photoreceptors is thought to mediate elevated ultraviolet sensitivity in a couple of other lizard species, SWS1 photoreceptor abundance remains low in this species. Instead, our findings suggest that short-wavelength sensitivity is driven by multiple factors which include a potentially red-shifted SWS1 photoreceptor and the absence of short-wavelength-absorbing oil droplets. Examining the coincidence of enhanced short-wavelength sensitivity with blue tongues among lizards of this genus will provide further insight into the co-evolution of conspecific signals and whole-eye spectral sensitivity.
Sex Differences in Energy Metabolism
Publisher: CRC Press
Date: 19-04-2016
DOI: 10.1201/B15365-6
The buzz around spatial resolving power and contrast sensitivity in the honeybee, Apis mellifera
Publisher: Elsevier BV
Date: 04-2020
Visual pigments in a palaeognath bird, the emu Dromaius novaehollandiae: Implications for spectral sensitivity and the origin of ultraviolet vision
Publisher: The Royal Society
Date: 13-07-2016
Abstract: A comprehensive description of the spectral characteristics of retinal photoreceptors in palaeognaths is lacking. Moreover, controversy exists with respect to the spectral sensitivity of the short-wavelength-sensitive-1 (SWS1) opsin-based visual pigment expressed in one type of single cone: previous microspectrophotometric (MSP) measurements in the ostrich ( Struthio camelus ) suggested a violet-sensitive (VS) SWS1 pigment, but all palaeognath SWS1 opsin sequences obtained to date (including the ostrich) imply that the visual pigment is ultraviolet-sensitive (UVS). In this study, MSP was used to measure the spectral properties of visual pigments and oil droplets in the retinal photoreceptors of the emu ( Dromaius novaehollandiae ). Results show that the emu resembles most other bird species in possessing four spectrally distinct single cones, as well as double cones and rods. Four cone and a single rod opsin are expressed, each an orthologue of a previously identified pigment. The SWS1 pigment is clearly UVS (wavelength of maximum absorbance [ λ max ] = 376 nm), with key tuning sites (Phe86 and Cys90) consistent with other vertebrate UVS SWS1 pigments. Palaeognaths would appear, therefore, to have UVS SWS1 pigments. As they are considered to be basal in avian evolution, this suggests that UVS is the most likely ancestral state for birds. The functional significance of a dedicated UVS cone type in the emu is discussed.
Visual pigment in the lens eyes of the box jellyfish Chiropsella bronzie
Publisher: The Royal Society
Date: 10-02-2010
Abstract: Box jellyfish (Cubomedusae) possess a unique visual system comprising 24 eyes of four morphological types. Moreover, box jellyfish display several visually guided behaviours, including obstacle avoidance and light-shaft attractance. It is largely unknown what kind of visual information box jellyfish use for carrying out these behaviours. Brightness contrast is almost certainly involved, but it is also possible that box jellyfish extract colour information from their surroundings. The possible presence of colour vision in box jellyfish has previously been investigated using behavioural, electrophysiological and immunohistochemical methods. However, the results from these studies are to some degree conflicting and inconclusive. Here, we present results from an investigation into the visual system of the box jellyfish Chiropsella bronzie , using microspectrophotometry and immunohistochemistry. Our results strongly indicate that only one type of visual pigment is present in the upper and lower lens eyes with a peak absorbance of approximately 510 nm. Additionally, the visual pigment appears to undergo bleaching, similar to that of vertebrate visual pigments.
The function of the sawfish's saw
Publisher: Elsevier BV
Date: 03-2012
Retinal adaptations of southern bluefin tuna larvae: Implications for culture
Publisher: Elsevier BV
Date: 05-2019
Comparative retinal anatomy in four species of elasmobranch
Publisher: Wiley
Date: 24-11-2011
DOI: 10.1002/JMOR.11033
Abstract: Using both light and transmission electron microscopy, we examined the retinal anatomy of four elasmobranch species with differing ecologies: the bull shark Carcharhinus leucas, Port Jackson shark Heterodontus portusjacksoni, epaulette shark Hemiscyllium ocellatum and pink whipray Himantura fai. Their retinas are typical of other vertebrates, having three nuclear and two synaptic layers, but are characterised by very large horizontal cells, low densities of ganglion cells (many of which are displaced to the inner nuclear and inner plexiform layers) and the presence of numerous myelinated axons within the nerve fibre layer. Carcharhinus leucas, H. fai and H. ocellatum have duplex retinas containing both rods and single cones. The peak ratio of rods to cones is much lower in C. leucas (4:1) and H. fai (3:1) compared to H. ocellatum (19:1), reflecting differences in diel activity patterns. No cones were observed in the retina of H. portusjacksoni, which is strongly nocturnal. The cones of H. fai lack a distinct myoid and their nuclei are located in a discrete layer sclerad to the external limiting membrane (ELM), whereas those of C. leucas and H. ocellatum have an obvious myoid, and their nuclei are located vitread to the ELM. No double/twin cones were observed in any species. Incorporating data from other studies, there is a clear correlation between rod outer segment volume and visual ecology in elasmobranchs, with smaller volumes found in partly diurnal pelagic species and larger volumes in benthic nocturnal species. This trend may reflect fundamental differences in visual temporal resolution between active and more sedentary species.
The distribution and abundance of electrosensory pores in two benthic sharks: a comparison of the wobbegong shark, Orectolobus maculatus, and the angel shark, Squatina australis
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/MF13213
Abstract: Electroreception is an ancient sense found in many aquatic animals, including sharks, which may be used in the detection of prey, predators and mates. Wobbegong sharks (Orectolobidae) and angel sharks (Squatinidae) represent two distantly related families that have independently evolved a similar dorso-ventrally compressed body form to complement their benthic ambush feeding strategy. Consequently, these groups represent useful models in which to investigate the specific morphological and physiological adaptations that are driven by the adoption of a benthic lifestyle. In this study, we compared the distribution and abundance of electrosensory pores in the spotted wobbegong shark (Orectolobus maculatus) with the Australian angel shark (Squatina australis) to determine whether both species display a similar pattern of clustering of sub-dermal electroreceptors and to further understand the functional importance of electroreception in the feeding behaviour of these benthic sharks. Orectolobus maculatus has a more complex electrosensory system than S. australis, with a higher abundance of pores and an additional cluster of electroreceptors positioned in the snout (the superficial ophthalmic cluster). Interestingly, both species possess a cluster of pores (the hyoid cluster, positioned slightly posterior to the first gill slit) more commonly found in rays, but which may be present in all benthic elasmobranchs to assist in the detection of approaching predators.
Nothing in (sponge) biology makes sense – except when based on holotypes
Publisher: Cambridge University Press (CUP)
Date: 04-05-2015
DOI: 10.1017/S0025315415000521
Abstract: Sponge species are infamously difficult to identify for non-experts due to their high morphological plasticity and the paucity of informative morphological characters. The use of molecular techniques certainly helps with species identification, but unfortunately it requires prior reference sequences. Holotypes constitute the best reference material for species identification, however their usage in molecular systematics and taxonomy is scarce and frequently not even attempted, mostly due to their antiquity and preservation history. Here we provide case studies in which we demonstrate the importance of using holotype material to answer phylogenetic and taxonomic questions. We also demonstrate the possibility of sequencing DNA fragments out of century-old holotypes. Furthermore we propose the deposition of DNA sequences in conjunction with new species descriptions.
Mimicry, colour forms and spectral sensitivity of the bluestriped fangblenny,Plagiotremus rhinorhynchos
Publisher: The Royal Society
Date: 25-02-2009
Abstract: Animals change their body coloration for a variety of purposes including communication, thermoregulation and crypsis. The cues that trigger adaptive colour change are often unclear, and the role of colour vision remains largely untested. Here, we investigated the bluestriped fangblenny ( Plagiotremus rhinorhynchos ), an aggressive mimic that changes its body coloration to impersonate a variety of coral reef fishes. In this field, we determined the fish species that the fangblenny associated with and measured the spectral reflectance of mimics and their models. We measured the spectral absorbance characteristics of the retinal photoreceptor visual pigments in the bluestriped fangblenny using microspectrophotometry and found it to have rod photoreceptors ( λ max 498 nm), single cones (449 nm) and double cones (561 nm principal member 520 nm accessory member). Using theoretical vision models, fangblennies could discriminate between the colours they adopted and the colours of the fish they associated with. Potential signal receivers ( Abudefduf abdominalis and Ctenochaetus strigosus ) perceived colours of most mimics to closely resemble fishes they associated with. However, fishes with ultraviolet-sensitive visual pigments were better at discriminating between mimics and models. Therefore, colour vision could be used by fangblennies when initiating colour change enabling them to accurately resemble fishes they associate with and to avoid detection by signal receivers.
Ontogenetic Changes in Retinal Ganglion Cell Distribution and Spatial Resolving Power in the Brown-Banded Bamboo Shark <b><i>Chiloscyllium punctatum</i></b> (Elasmobranchii)
Publisher: S. Karger AG
Date: 2014
DOI: 10.1159/000361036
Abstract: The development of the visual system in b /b anamniotic vertebrates is a continual process, allowing for ontogenetic changes in retinal topography and spatial resolving power. We examined the number and distribution of retinal ganglion cells in wholemounted retinae throughout the protracted embryonic development (∼5 months) of a chondrichthyan, i.e. the brown-banded bamboo shark i Chiloscyllium punctatum, /i from the beginning of retinal cell differentiation (approximately halfway through embryogenesis) to adulthood. We also identified and quantified the number of apoptosed cells within the ganglion cell layer to evaluate the contribution of apoptosis to changes in retinal topography. i C. punctatum /i undergoes rapid changes in ganglion cell distribution during embryogenesis, where high levels of apoptosis, especially around the retinal periphery, result in relative increases in ganglion cell density in the central retina which progressively extend nasally and temporally to form a meridional band at hatching. After hatching, i C. punctatum /i forms and maintains a horizontal streak, showing only minor changes in topography during growth, with basal levels of apoptosis. The total number of retinal ganglion cells reaches 547,881 in adult sharks, but the mean (3,228 cells·mm sup -2 /sup ) and peak (4,983 cells·mm sup -2 /sup ) retinal ganglion cell densities are highest around the time of hatching. Calculated estimates of spatial resolving power, based on ganglion cell spacing (assuming a hexagonal mosaic) and assessment of the focal length from cryosections of the eye, increase from 1.47 cycles·degree sup -1 /sup during embryogenesis to 4.29 cycles·degree sup -1 /sup in adults. The increase in spatial resolving power across the retinal meridian would allow this species to hunt and track faster, more mobile prey as it reaches maturity.
Underwater hearing in sea snakes (Hydrophiinae): first evidence of auditory evoked potential thresholds
Publisher: The Company of Biologists
Date: 15-07-2019
DOI: 10.1242/JEB.198184
Abstract: The viviparous sea snakes (Hydrophiinae) are a secondarily aquatic radiation of more than 60 species that possess many phenotypic adaptations to marine life. However, virtually nothing is known of the role and sensitivity of hearing in sea snakes. This study investigated the hearing sensitivity of the fully marine sea snake Hydrophis stokesii by measuring auditory evoked potential (AEP) audiograms for two in iduals. AEPs were recorded from 40 Hz (the lowest frequency tested) up to 600 Hz, with a peak in sensitivity identified at 60 Hz (163.5 dB re. 1 µPa or 123 dB re. 1 µm s−2). Our data suggest that sea snakes are sensitive to low-frequency sounds but have relatively low sensitivity compared with bony fishes and marine turtles. Additional studies are required to understand the role of sound in sea snake life history and further assess these species' vulnerability to anthropogenic noise.
Survival of the Stillest: Predator Avoidance in Shark Embryos
Publisher: Public Library of Science (PLoS)
Date: 09-01-2013
Photoreceptor types, visual pigments, and topographic specializations in the retinas of hydrophiid sea snakes
Publisher: Wiley
Date: 07-02-2012
DOI: 10.1002/CNE.22784
Abstract: Sea snakes have evolved numerous anatomical, physiological, and behavioral adaptations to suit their wholly aquatic lifestyle. However, although sea snakes use vision for foraging and mate selection, little is known about their visual abilities. We used microspectrophotometry, light microscopy, and scanning electron microscopy to characterize the retinal photoreceptors of spine-bellied (Lapemis curtus) and horned (Acalyptophis peronii) sea snakes. Both species have three types of visual pigment sensitive to short (SWS wavelength of maximum absorbance, λmax 428-430 nm), medium (MWS λmax 496 nm), and long wavelengths of light (LWS λmax 555-559 nm) in each of three different subtypes of cone-like single photoreceptor. They also possess a cone-like double photoreceptor subtype, both the principal and accessory member of which contain the LWS visual pigment. Conventional rods were not observed, although the MWS photoreceptor may be a "transmuted" rod. We also used stereology to measure the total number and topographic distribution of neurons in the ganglion cell layer of L. curtus, the olive sea snake (Aipysurus laevis), and the olive-headed sea snake (Disteira major). All species have a horizontal visual streak with specialized areas in the nasal and temporal retina. Both L. curtus and D. major also have a specialized area in the ventral retina, which may reflect differences in habitat usage and/or foraging behavior compared to A. laevis. Maximal spatial resolution was estimated at 1.1, 1.6, and 2.3 cycles deg⁻¹ in D. major, L. curtus, and A. laevis, respectively the superior value for A. laevis may reflect its specialized crevice-foraging hunting technique.
Evolution of Vertebrate Phototransduction: Cascade Activation
Publisher: Oxford University Press (OUP)
Date: 11-05-2016
Barcoding Sponges: An Overview Based on Comprehensive Sampling
Publisher: Public Library of Science (PLoS)
Date: 03-07-2012
Assessing the use of genomic DNA as a predictor of the maximum absorbance wavelength of avian SWS1 opsin visual pigments
Publisher: Springer Science and Business Media LLC
Date: 02-12-2008
DOI: 10.1007/S00359-008-0395-2
Abstract: Recently, in vitro mutation studies have made it possible to predict the wavelengths of maximum absorbance (lambdamax) of avian UV/violet sensitive visual pigments (SWS1) from the identity of a few key amino acid residues in the opsin gene. Given that the absorbance spectrum of a cone's visual pigment and of its pigmented oil droplet can be predicted from just the lambdamax, it may become possible to predict the entire spectral sensitivity of a bird using genetic s les from live birds or museum specimens. However, whilst this concept is attractive, it must be validated to assess the reliability of the predictions of lambdamax from opsin amino acid sequences. In this paper, we have obtained partial sequences covering three of the known spectral tuning sites in the SWS1 opsin and predicted lambdamax of all bird species for which the spectral absorbance has been measured using microspectrophotometry. Our results validate the use of molecular data from genomic DNA to predict the gross differences in lambdamax between the violet- and ultraviolet-sensitive subtypes of SWS1 opsin. Additionally, we demonstrate that a bird, the bobolink Dolichonyx oryzivorus L., can have more than one SWS1 visual pigment in its retina.
The Visual Ecology of Avian Photoreceptors
Publisher: Elsevier BV
Date: 09-2001
DOI: 10.1016/S1350-9462(01)00009-X
Abstract: The spectral sensitivities of avian retinal photoreceptors are examined with respect to microspectrophotometric measurements of single cells, spectrophotometric measurements of extracted or in vitro regenerated visual pigments, and molecular genetic analyses of visual pigment opsin protein sequences. Bird species from erse orders are compared in relation to their evolution, their habitats and the multiplicity of visual tasks they must perform. Birds have five different types of visual pigment and seven different types of photoreceptor-rods, double (uneven twin) cones and four types of single cone. The spectral locations of the wavelengths of maximum absorbance (lambda(max)) of the different visual pigments, and the spectral transmittance characteristics of the intraocular spectral filters (cone oil droplets) that also determine photoreceptor spectral sensitivity, vary according to both habitat and phylogenetic relatedness. The primary influence on avian retinal design appears to be the range of wavelengths available for vision, regardless of whether that range is determined by the spectral distribution of the natural illumination or the spectral transmittance of the ocular media (cornea, aqueous humour, lens, vitreous humour). Nevertheless, other variations in spectral sensitivity exist that reflect the variability and complexity of avian visual ecology.
From crypsis to mimicry: changes in colour and the configuration of the visual system during ontogenetic habitat transitions in a coral reef fish
Publisher: The Company of Biologists
Date: 2016
DOI: 10.1242/JEB.139501
Abstract: Animals often change their habitat throughout ontogeny yet, the triggers for habitat transitions and how these correlate with developmental changes – e.g. physiological, morphological, and behavioural – remain largely unknown. Here, we investigated how ontogenetic changes in body colouration and of the visual system relate to habitat transitions in a coral-reef fish. Adult dusky dottybacks, Pseudochromis fuscus, are aggressive mimics that change colour to imitate various fishes in their surroundings however, little is known about the early life stages of this fish. Using a developmental time-series in combination with the examination of wild caught specimens we uncover that dottybacks change colour twice during development: (i) nearly translucent cryptic pelagic larvae change to a grey camouflage colouration when settling on coral reefs and (ii) juveniles change to mimic yellow or brown coloured fishes when reaching a size capable of consuming juvenile fish prey. Moreover, microspectrophotometric (MSP) and quantitative real time PCR (qRT-PCR) experiments show developmental changes of the dottyback visual system, including the use of a novel adult specific visual gene (RH2 opsin). This gene is likely to be coexpressed with other visual pigments to form broad spectral sensitivities that cover the medium-wavelength part of the visible spectrum. Surprisingly, the visual modifications precede changes in habitat and colour, possibly because dottybacks need to first acquire the appropriate visual performance before transitioning into novel life stages.
Sensory Rewiring in an Echolocator: Genome-Wide Modification of Retinogenic and Auditory Genes in the Bat Myotis davidii
Publisher: Oxford University Press (OUP)
Date: 10-2014
Abstract: Bats comprise 20% of all mammalian species and display a number of characteristics, including true flight, echolocation, and a heightened ability to resist viral load that uniquely position this group for comparative genomic studies. Here we searched for evidence of genomic variation consistent with sensory rewiring through bat evolution. We focused on two species with ergent sensory preferences. Myotis davidii is a bat species that echolocates and possesses dim- but not daylight-adapted vision whereas the black flying fox (Pteropus alecto) has highly developed day vision but does not echolocate. Using the naked mole rat as a reference, we found five functional genes (CYP1A2, RBP3, GUCY2F, CRYBB1, and GRK7) encoding visual proteins that have degenerated into pseudogenes in M. davidii but not P. alecto. In a second approach genome-wide codon usage bias (CUB) was compared between the two bat species. This CUB ranking systematically enriched for vision-related (CLN8, RD3, IKZF1, LAMC3, CRX, SOX8, VAX2, HPS1, RHO, PRPH2, and SOX9) and hearing-related (TPRN, TMIE, SLC52A3, OTOF, WFS1, SOD1, TBX18, MAP1A, OTOS, GPX1, and USH1G) machinery in M. davidii but not P. alecto. All vision and hearing genes selectively enriched in M. davidii for which orthologs could be identified also were more biased in the echolocating M. lucifugus than the nonecholocating P. v yrus. We suggest that the existence of codon bias in vision- and hearing-related genes in a species that has evolved echolocation implies CUB is part of evolution’s toolkit to rewire sensory systems. We propose that the two genetic changes (pseudogene formation and CUB) collectively paint a picture of that incorporates a combination of destruction and gain-of-function. Together, they help explain how natural selection has reduced physiological costs associated with the development of a smaller eye poorly adapted to day vision but that also contribute to enhanced dim light vision and the hearing adaptations consonant with echolocation.
Aquatic prey use countershading camouflage to match the visual background
Publisher: Oxford University Press (OUP)
Date: 10-07-2017
Retinal topography and spectral sensitivity of the Port Jackson shark (Heterodontus portusjacksoni )
Publisher: Wiley
Date: 11-04-2020
DOI: 10.1002/CNE.24911
Deceptive Desmas: Molecular Phylogenetics Suggests a New Classification and Uncovers Convergent Evolution of Lithistid Demosponges
Publisher: Public Library of Science (PLoS)
Date: 07-01-2015
Visual ecology of the Australian lungfish (Neoceratodus forsteri)
Publisher: Springer Science and Business Media LLC
Date: 2008
Scene from above: Retinal ganglion cell topography and spatial resolving power in the giraffe (Giraffa camelopardalis)
Publisher: Wiley
Date: 18-04-2013
DOI: 10.1002/CNE.23271
Abstract: The giraffe (Giraffa camelopardalis) is a browser that uses its extensible tongue to selectively collect leaves during foraging. As the tallest extant terrestrial mammal, its elevated head height provides panoramic surveillance of the environment. These aspects of the giraffe's ecology and phenotype suggest that vision is of prime importance. Using Nissl-stained retinal wholemounts and stereological methods, we quantitatively assessed the retinal specializations in the ganglion cell layer of the giraffe. The mean total number of retinal ganglion cells was 1,393,779 and their topographic distribution revealed the presence of a horizontal visual streak and a temporal area. With a mean peak of 14,271 cells/mm(2), upper limits of spatial resolving power in the temporal area ranged from 25 to 27 cycles/degree. We also observed a dorsotemporal extension (anakatabatic area) that tapers toward the nasal retina giving rise to a complete dorsal arch. Using neurofilament-200 immunohistochemistry, we also detected a dorsal arch formed by alpha ganglion cells with density peaks in the temporal (14-15 cells/mm(2)) and dorsonasal (10 cells/mm(2)) regions. As with other artiodactyls, the giraffe shares the presence of a horizontal streak and a temporal area which, respectively, improve resolution along the horizon and in the frontal visual field. The dorsal arch is related to the giraffe's head height and affords enhanced resolution in the inferior visual field. The alpha ganglion cell distribution pattern is unique to the giraffe and enhances acquisition of motion information for the control of tongue movement during foraging and the detection of predators.
Visual pigments, oil droplets, ocular media and cone photoreceptor distribution in two species of passerine bird: the blue tit ( Parus caeruleus L.) and the blackbird ( Turdus merula L.)
Publisher: Springer Science and Business Media LLC
Date: 25-04-2000
Abstract: The spectral absorption characteristics of the retinal photoreceptors of the blue tit (Parus caeruleus) and blackbird (Turdus merula) were investigated using microspectrophotometry. The retinae of both species contained rods, double cones and four spectrally distinct types of single cone. Whilst the visual pigments and cone oil droplets in the other receptor types are very similar in both species, the wavelength of maximum sensitivity (lambda(max)) of long-wavelength-sensitive single and double cone visual pigment occurs at a shorter wavelength (557 nm) in the blackbird than in the blue tit (563 nm). Oil droplets located in the long-wavelength-sensitive-single cones of both species cut off wavelengths below 570-573 nm, theoretically shifting cone peak spectral sensitivity some 40 nm towards the long-wavelength end of the spectrum. This raises the possibility that the precise lambda(max) of the long-wavelength-sensitive visual pigment is optimised for the visual function of the double cones. The distribution of cone photoreceptors across the retina, determined using conventional light and fluorescence microscopy, also varies between the two species and may reflect differences in their visual ecology.
Photon hunting in the twilight zone: Visual features of mesopelagic bioluminescent sharks
Publisher: Public Library of Science (PLoS)
Date: 06-08-2014
Modelling oil droplet absorption spectra and spectral sensitivities of bird cone photoreceptors
Publisher: Springer Science and Business Media LLC
Date: 15-02-2005
DOI: 10.1007/S00359-004-0595-3
Abstract: Birds have four spectrally distinct types of single cones that they use for colour vision. It is often desirable to be able to model the spectral sensitivities of the different cone types, which vary considerably between species. However, although there are several mathematical models available for describing the spectral absorption of visual pigments, there is no model describing the spectral absorption of the coloured oil droplets found in three of the four single cone types. In this paper, we describe such a model and illustrate its use in estimating the spectral sensitivities of single cones. Furthermore, we show that the spectral locations of the wavelengths of maximum absorbance (lambda(max)) of the short- (SWS), medium- (MWS) and long- (LWS) wavelength-sensitive visual pigments and the cut-off wavelengths (lambda(cut)) of their respective C-, Y- and R-type oil droplets can be predicted from the lambda(max) of the ultraviolet- (UVS)/violet- (VS) sensitive visual pigment.
Visual resolution and contrast sensitivity in two benthic sharks
Publisher: The Company of Biologists
Date: 2016
DOI: 10.1242/JEB.132100
Abstract: Sharks have long been described as having ‘poor’ vision. They are cone monochromats and anatomical estimates suggest they have low spatial resolution. However, there are no direct behavioural measurements of spatial resolution or contrast sensitivity. This study estimates contrast sensitivity and spatial resolution of two species of benthic sharks, the Port Jackson shark, Heterodontus portusjacksoni, and the brown-banded bamboo shark, Chiloscyllium punctatum, by recording eye movements in response to optokinetic stimuli. Both species tracked moving low spatial frequency gratings with weak but consistent eye movements. Eye movements ceased at 0.38 cycles per degree, even for high contrasts, suggesting low spatial resolution. However, at lower spatial frequencies, eye movements were elicited by low contrast gratings, 1.3 % and 2.9% contrast in H. portusjacksoni and C. punctatum respectively. Contrast sensitivity was higher than in other vertebrates with a similar spatial resolving power, which may reflect an adaptation to the relatively low contrast encountered in aquatic environments. Optokinetic gain was consistently low and neither species stabilised the gratings on their retina. In order to check whether restraining the animals affected their optokinetic responses, we also analysed eye movements in free-swimming C. punctatum. We found no eye movements that could compensate for body rotations suggesting that vision may pass through phases of stabilisation and blur during swimming. As C. punctatum is a sedentary benthic species, gaze stabilization during swimming may not be essential. Our results suggest that vision in sharks is not ‘poor’ as previously suggested, but optimised for contrast detection rather than spatial resolution.
Visual Specializations in Five Sympatric Species of Stingrays from the Family Dasyatidae
Publisher: S. Karger AG
Date: 2015
DOI: 10.1159/000381091
Abstract: The eyes of five ray species i (Taeniura lymma /i , i Neotrygon kuhlii /i , i Pastinachus atrus /i , i Himantura uarnak /i and i Urogymnus asperrimus) /i from the same taxonomic family (Dasyatidae) and the same geographic region (Ningaloo Reef, Western Australia) were studied to identify differences in retinal specializations that may reflect niche specialization. The topographic distributions of photoreceptors (rods and all cones) and ganglion cells were assessed and used to identify localized peaks in cell densities that indicate specializations for acute vision. These data were also used to calculate summation ratios of photoreceptors to ganglion cells in each species and estimate the anatomical spatial resolving power of the eye. Subtle differences in the distribution of retinal neurons appear to be related to the ecology of these closely related species of stingrays. The main specialization in the retinal cell density distribution is the dorsal streak that allows these animals to scan the substrate for potential prey. The blue-spotted fantail ray, i T. lymma /i , showed the highest peak density of rods (86,700 rods mm sup -2 /sup ) suggesting a specialization for scotopic vision. The highest peak density of cones (9,970 cones mm sup -2 /sup ) was found in i H. uarnak, /i and the highest peak density of ganglion cells (4,500 cells mm sup -2 /sup ) was found in i P. atrus /i . The proportion of rods to cones in the dorsal streak was higher in the two smaller species (12.5-14:1 in i T. lymma /i and i N. kuhlii /i ) than the larger stingrays (6-8:1 in i P. atrus /i , i H. uarnak /i and i U. asperrimus /i ). Visual specializations in different sympatric species are subtle but may reflect specializations to specific ecological niches.
Sharks senses and shark repellents
Publisher: Wiley
Date: 2015
Abstract: Despite over 70 years of research on shark repellents, few practical and reliable solutions to prevent shark attacks on humans or reduce shark bycatch and depredation in commercial fisheries have been developed. In large part, this deficiency stems from a lack of fundamental knowledge of the sensory cues that drive predatory behavior in sharks. However, the widespread use of shark repellents is also h ered by the physical constraints and technical or logistical difficulties of deploying substances or devices in an open-water marine environment to prevent an unpredictable interaction with a complex animal. Here, we summarize the key attributes of the various sensory systems of sharks and highlight residual knowledge gaps that are relevant to the development of effective shark repellents. We also review the most recent advances in shark repellent technology within the broader historical context of research on shark repellents and shark sensory systems. We conclude with suggestions for future research that may enhance the efficacy of shark repellent devices, in particular, the continued need for basic research on shark sensory biology and the use of a multi-sensory approach when developing or deploying shark repellent technology.
Vision and photoentrainment in fishes: The effects of natural and anthropogenic perturbation
Publisher: Wiley
Date: 2015
Abstract: Vision and photoentrainment in fishes are vital for feeding, avoiding predation, spatial orientation, navigation, social communication and the synchronization of many homeostatic functions such as activity patterns and sleep. The camera-like (image-forming) eyes of fishes are optimized to provide a clear view of their preferred ecological niche, while non-visual photoreceptors provide irradiance detection that mediates circadian photoentrainment, an endogenous time-keeping mechanism (biological clock) to respond to predictable changes in environmental conditions. Fish and fisheries are under pressure from both natural and anthropogenic perturbation, which in many cases alters the intensity and spectral composition of the light environment on which they depend for their survival. This review examines the effects of a changing light environment and turbidity on the health of fishes within a developmental and ecological context. Understanding the sensory environment of fishes is vital to predicting their responses and, ultimately, their resilience to environmental change and the potential for maintaining sustainable levels of bio ersity.
Does Lepidopteran Larval Crypsis Extend into the Ultraviolet?
Publisher: Springer Science and Business Media LLC
Date: 28-04-1998
It is not just size that matters
Publisher: Springer Science and Business Media LLC
Date: 05-05-2015
A spitting image: specializations in archerfish eyes for vision at the interface between air and water
Publisher: The Royal Society
Date: 14-04-2010
Abstract: Archerfish are famous for spitting jets of water to capture terrestrial insects, a task that not only requires oral dexterity, but also the ability to detect small camouflaged prey against a visually complex background of overhanging foliage. Because detection of olfactory, auditory and tactile cues is diminished at air–water interfaces, archerfish must depend almost entirely on visual cues to mediate their sensory interactions with the aerial world. During spitting, their eyes remain below the water's surface and must adapt to the optical demands of both aquatic and aerial fields of view. These challenges suggest that archerfish eyes may be specially adapted to life at the interface between air and water. Using microspectrophotometry to characterize the spectral absorbance of photoreceptors, we find that archerfish have differentially tuned their rods and cones across their retina, correlated with spectral differences in aquatic and aerial fields of view. Spatial resolving power also differs for aquatic and aerial fields of view with maximum visual resolution (6.9 cycles per degree) aligned with their preferred spitting angle. These measurements provide insight into the functional significance of intraretinal variability in archerfish and infer intraretinal variability may be expected among surface fishes or vertebrates where different fields of view vary markedly.
Retinal asymmetry in birds
Publisher: Elsevier BV
Date: 2000
DOI: 10.1016/S0960-9822(00)00297-9
Abstract: Vertebrate sensory systems are generally based on bilaterally symmetrical sense organs. It is evident, nevertheless, that birds preferentially use either their left or right eye for viewing novel or familiar stimuli [1], and perform visual discrimination tasks under monocular viewing conditions better with one eye than with the other [2] [3]. Because of the nearly complete contralateral decussation of the optic nerves in birds [4], it has been assumed that this ision of labour is due solely to cerebral hemispheric specialisation, generated as a result of uneven photostimulation of the eyes of the developing embryo during the last three or four days before hatching [5] [6]. Here, however, we present evidence that in the European starling, Sturnus vulgaris, even the retinae are morphologically asymmetrical in terms of photoreceptor distribution. This is the first evidence for such asymmetry in any bird and suggests that retinal photoreceptor composition should be assessed during studies involving the lateralisation of visually mediated behaviours.
Enhanced short-wavelength sensitivity in the blue-tongued skink, Tiliqua rugosa
Publisher: Cold Spring Harbor Laboratory
Date: 27-03-2022
DOI: 10.1101/2022.03.25.485754
Abstract: The complex visually mediated behaviors of diurnal lizards are enabled by a retina typically containing five types of opsins with the potential for tetrachromatic color vision. Despite lizards using a wide range of color signals, the limited variation in photoreceptor spectral sensitivities across lizards suggests only weak selection for species-specific, spectral tuning of photoreceptors. Some species, however, have enhanced short wavelength sensitivity, which likely helps with the detection of signals rich in ultraviolet and short wavelengths. In this study, we examined the visual system of Tiliqua rugosa , which has a UV/blue tongue, to determine the spectral sensitivity of the eye and to gain insight into this species’ visual ecology. Electroretinograms coupled with spectral stimulation showed peak sensitivity at 560 nm with high similarity to other lizards at wavelengths greater than 530 nm. However, at shorter wavelengths, sensitivity is enhanced leading to a spectral sensitivity curve that is 28 nm broader (full width at half height) than other lizards studied so far. The width of the curve is partially explained by a population of photoreceptors that respond more strongly to low temporal frequencies with possible peaks in sensitivity between 460 and 470 nm suggesting that they are SWS2 photoreceptors. The lack of a peak in sensitivity at 360 nm at low temporal frequencies and under a monochromatic light that suppresses the response of LWS photoreceptors, suggests that the SWS1 photoreceptors are red-shifted. In addition, the yellow and green oil droplets that are common in other diurnal lizards appear to be missing and instead, only transparent and pale-yellow oil droplets are present. LWS photoreceptors are likely paired with pale-yellow oil droplets to produce LWS photoreceptors with wider spectral sensitivity curves than in other lizards. Opsin sequencing reveals SWS1, SWS2, RH1, RH2 and LWS opsin genes that are very similar to the visual opsins detected in the green anole, Anolis carolinensis , suggesting there is little change in the spectral sensitivity of photoreceptors compared to other diurnal lizards. Since we only obtained a partial sequence of the SWS1 opsin, we were unable to determine whether amino acid substitution at tuning sites could have played a role in red-shifting the SWS1 photoreceptor spectral sensitivity. Photoreceptor densities are typically higher in central and ventral retinal regions than in the dorsal retina suggesting that higher spatial s ling is necessary at eye level and above the animal than on the ground. However, the SWS1 photoreceptors do not follow this pattern potentially due to their low abundance making them less relevant to high acuity visual tasks. Our findings demonstrate that there are possibly multiple mechanisms acting synergistically in the visual system of T. rugosa to enhance short wavelength sensitivity between 360 and 530 nm. While it is tempting to suggest that this is an adaptation to facilitate the detection of the blue tongues of conspecifics, additional experiments are necessary to determine its ecological relevance. Color vision and the distribution of photoreceptor subtypes in T. rugosa
Visual pigments, cone oil droplets and ocular media in four species of estrildid finch
Publisher: Springer Science and Business Media LLC
Date: 10-06-2000
Abstract: A microspectrophotometric study was conducted on the retinal photoreceptors of four species of bird: cut-throat finches (Amadina fasciata), gouldian finches (Erythrura gouldiae), white-headed munias (Lonchura maja) and plum-headed finches (Neochmia modesta). Spectral characteristics of the photoreceptors in all four species were very similar. Rods contained a medium-wavelength-sensitive visual pigment with a wavelength of maximum absorbance at 502-504 nm. Four spectrally distinct types of single cone contained a visual pigment with wavelength of maximum absorbance at either 370-373 nm (ultraviolet-sensitive), 440-447 nm (short-wavelength-sensitive) 500 nm (medium-wavelength-sensitive) or 562-565 nm (long-wavelength-sensitive). Oil droplets in the ultraviolet-sensitive single cones showed no detectable absorption between 330 nm and 800 nm. Oil droplets in the short-, medium-, and long-wavelength-sensitive single cones had cut-off wavelengths at 415-423 nm, 510-520 nm and 567-575 nm, respectively. Double cones contained the visual pigment with wavelength of maximum absorbance at 562-565 nm observed in long-wavelength-sensitive single cones. Only the principal member of the double cone pair contained an oil droplet (P-type, cut-off wavelength at 414-489 nm depending on species and retinal location). Spectral transmittance of the intact ocular media of each species was measured along the optic axis. Wavelengths of 0.5 transmittance for all species were very similar (316-318 nm).
Near infrared light reduces oxidative stress and preserves function in CNS tissue vulnerable to secondary degeneration following partial transection of the optic nerve
Publisher: Mary Ann Liebert Inc
Date: 11-2010
Abstract: Traumatic injury to the central nervous system (CNS) is accompanied by the spreading damage of secondary degeneration, resulting in further loss of neurons and function. Partial transection of the optic nerve (ON) has been used as a model of secondary degeneration, in which axons of retinal ganglion cells in the ventral ON are spared from initial dorsal injury, but are vulnerable to secondary degeneration. We have recently demonstrated that early after partial ON injury, oxidative stress spreads through the ventral ON vulnerable to secondary degeneration via astrocytes, and persists in the nerve in aggregates of cellular debris. In this study, we show that diffuse transcranial irradiation of the injury site with far red to near infrared (NIR) light (WARP 10 LED array, center wavelength 670 nm, irradiance 252 W/m(-2), 30 min exposure), as opposed to perception of light at this wavelength, reduced oxidative stress in areas of the ON vulnerable to secondary degeneration following partial injury. The WARP 10 NIR light treatment also prevented increases in NG-2-immunopositive oligodendrocyte precursor cells (OPCs) that occurred in ventral ON as a result of partial ON transection. Importantly, normal visual function was restored by NIR light treatment with the WARP 10 LED array, as assessed using optokinetic nystagmus and the Y-maze pattern discrimination task. To our knowledge, this is the first demonstration that 670-nm NIR light can reduce oxidative stress and improve function in the CNS following traumatic injury in vivo.
Ontogenetic changes in spectral sensitivity and retinal topography in the retina of the yellowtail kingfish (Seriola lalandi): Implications for the global Seriola aquaculture industry
Publisher: Elsevier BV
Date: 05-2017
Not all electric shark deterrents are made equal: Effects of a commercial electric anklet deterrent on white shark behaviour
Publisher: Public Library of Science (PLoS)
Date: 11-03-2019
Behavioural evidence for colour vision in an elasmobranch
Publisher: The Company of Biologists
Date: 15-12-2011
DOI: 10.1242/JEB.061853
Abstract: Little is known about the sensory abilities of elasmobranchs (sharks, skates and rays) compared with other fishes. Despite their role as apex predators in most marine and some freshwater habitats, interspecific variations in visual function are especially poorly studied. Of particular interest is whether they possess colour vision and, if so, the role(s) that colour may play in elasmobranch visual ecology. The recent discovery of three spectrally distinct cone types in three different species of ray suggests that at least some elasmobranchs have the potential for functional trichromatic colour vision. However, in order to confirm that these species possess colour vision, behavioural experiments are required. Here, we present evidence for the presence of colour vision in the giant shovelnose ray (Glaucostegus typus) through the use of a series of behavioural experiments based on visual discrimination tasks. Our results show that these rays are capable of discriminating coloured reward stimuli from other coloured (unrewarded) distracter stimuli of variable brightness with a success rate significantly different from chance. This study represents the first behavioural evidence for colour vision in any elasmobranch, using a paradigm that incorporates extensive controls for relative stimulus brightness. The ability to discriminate colours may have a strong selective advantage for animals living in an aquatic ecosystem, such as rays, as a means of filtering out surface-wave-induced flicker.
Vision in sharks and rays: Opsin diversity and colour vision
Publisher: Elsevier BV
Date: 10-2020
Morphological Indicators of Olfactory Capability in Wobbegong Sharks (Orectolobidae, Elasmobranchii)
Publisher: S. Karger AG
Date: 2009
DOI: 10.1159/000209865
Abstract: Elasmobranchs are thought to possess an acute sense of smell, but the relationship between the anatomy of their olfactory organs and their sensory ecology is poorly understood. Moreover, the ecological ersity of elasmobranchs as a group indicates that there might be considerable interspecific variation in the importance of the olfactory sense. Wobbegong sharks, with their sedentary lifestyle and ambush predatory technique, probably utilize their senses differently than other shark species, making it difficult to generalize about their olfactory capabilities and olfaction-dependent behaviors. In this study, the number of olfactory lamellae and the surface area of the olfactory epithelium were measured as a means of assessing relative olfactory sensitivity in four species of wobbegong shark (the Western wobbegong, i Orectolobus hutchinsi /i the spotted wobbegong, i O. maculatus /i the ornate wobbegong, i O. ornatus /i and the dwarf spotted wobbegong, i O. parvimaculatus /i ). We also present a phylogenetic comparative analysis between wobbegongs and other elasmobranchs for which published data on olfactory morphology are available. There is a significant difference in the total number of olfactory lamellae between most species, but not between i O. hutchinsi /i and i O. maculatus /i , although the olfactory sensory surface area is comparable between these two species and i O. ornatus /i . i Orectolobus parvimaculatus /i has a significantly larger olfactory sensory surface area than the other three species, and there is a positive relationship between total body length and olfactory sensory surface area for all four species. Assuming that these morphological measures are true indications of olfactory capability, the olfactory abilities of wobbegongs are as good as, or better than, other benthic elasmobranchs. Interspecific differences in olfactory ability within this group of benthic ambush predators could indicate relative differences in prey detection, intraspecific recognition and mate detection.
Retinal temporal resolution and contrast sensitivity in the parasitic lampreyMordacia mordaxand its non-parasitic derivativeM.praecox
Publisher: The Company of Biologists
Date: 2017
DOI: 10.1242/JEB.150383
Abstract: L reys and hagfishes are the sole extant representatives of the early agnathan (jawless) vertebrates. We compared retinal function of fully-metamorphosed, immature Mordacia mordax (which are about to commence parasitic feeding) with those of sexually-mature in iduals of its non-parasitic derivative M. praecox. We focused on elucidating the retinal adaptations to dim-light environments in these nocturnally-active l reys, using electroretinography to determine the temporal resolution (flicker fusion frequency, FFF) and temporal contrast sensitivity (CS) of enucleated eyecups at different temperatures and light intensities. FFF was significantly affected by temperature and light intensity. Critical flicker fusion frequency (cFFF, the highest FFF recorded) of M. praecox and M. mordax increased from 15.1 and 21.8 Hz at 9°C to 31.1 and 36.9 Hz at 24°C, respectively. CS of both species increased by an order of magnitude between 9 and 24°C, but remained comparatively constant across all light intensities. Although FFF values for Mordacia spp. are relatively low, retinal responses showed a particularly high contrast sensitivity of 625 in M. praecox and 710 in M. mordax at 24°C. This suggests selective pressures favour low temporal resolution and high contrast sensitivity in both species, thereby enhancing the capture of photons and increasing sensitivity in their light-limited environments. FFF indicated all retinal photoreceptors exhibit the same temporal response. Although the slow response kinetics (i.e., low FFF) and saturation of the response at bright light intensities characterise the photoreceptors of both species as rod-like, it is unusual for such a photoreceptor to be functional under scotopic and photopic conditions.
The Role of the Voltage-Gated Potassium Channel Proteins Kv8.2 and Kv2.1 in Vision and Retinal Disease: Insights from the Study of Mouse Gene Knock-Out Mutations
Publisher: Society for Neuroscience
Date: 2019
DOI: 10.1523/ENEURO.0032-19.2019
Abstract: Mutations in the KCNV2 gene, which encodes the voltage-gated K + channel protein Kv8.2, cause a distinctive form of cone dystrophy with a supernormal rod response (CDSRR). Kv8.2 channel subunits only form functional channels when combined in a heterotetramer with Kv2.1 subunits encoded by the KCNB1 gene. The CDSRR disease phenotype indicates that photoreceptor adaptation is disrupted. The electroretinogram (ERG) response of affected in iduals shows depressed rod and cone activity, but what distinguishes this disease is the supernormal rod response to a bright flash of light. Here, we have utilized knock-out mutations of both genes in the mouse to study the pathophysiology of CDSRR. The Kv8.2 knock-out (KO) mice show many similarities to the human disorder, including a depressed a-wave and an elevated b-wave response with bright light stimulation. Optical coherence tomography (OCT) imaging and immunohistochemistry indicate that the changes in six-month-old Kv8.2 KO retinae are largely limited to the outer nuclear layer (ONL), while outer segments appear intact. In addition, there is a significant increase in TUNEL - positive cells throughout the retina. The Kv2.1 KO and double KO mice also show a severely depressed a-wave, but the elevated b-wave response is absent. Interestingly, in all three KO genotypes, the c-wave is totally absent. The differential response shown here of these KO lines, that either possess homomeric channels or lack channels completely, has provided further insights into the role of K + channels in the generation of the a-, b-, and c-wave components of the ERG.
Related Organisations
University Of Bristol
Location: United Kingdom of Great Britain and Northern Ireland
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