Retinal characteristics of the ornate dragon lizard, <i>Ctenophorus ornatus</i>

Barbour, Helen; Archer, Michael A.; Hart, Nathan S.; Thomas, Nicole; Dunlop, Sarah; Beazley, Lyn; Shand, Julia

doi:10.1002/cne.10308

Cited by 69 publications

(87 citation statements)

References 57 publications

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“…Previous studies based on a single technique have sometimes yielded contradictory results. For example, in the ornate dragon lizard, Ctenophorus ornatus (Agamidae), results of a behavioural test suggested UV vision (LeBas and Marshall, 2000), but MSP measurements later indicated that this species lacks UVS photoreceptors and is therefore blind to UV wavelengths (Barbour et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

Ultraviolet vision in lacertid lizards: evidence from retinal structure, eye transmittance, SWS1 visual pigment genes, and behaviour

Lanuza

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2014

Journal of Experimental Biology

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Ultraviolet (UV) vision and UV colour patches have been reported in a wide range of taxa and are increasingly appreciated as an integral part of vertebrate visual perception and communication systems. Previous studies with Lacertidae, a lizard family with diverse and complex coloration, have revealed the existence of UV-reflecting patches that may function as social signals. However, confirmation of the signalling role of UV coloration requires demonstrating that the lizards are capable of vision in the UV waveband. Here we use a multidisciplinary approach to characterize the visual sensitivity of a diverse sample of lacertid species. Spectral transmission measurements of the ocular media show that wavelengths down to 300 nm are transmitted in all the species sampled. Four retinal oil droplet types can be identified in the lacertid retina. Two types are pigmented and two are colourless. Fluorescence microscopy reveals that a type of colourless droplet is UV-transmitting and may thus be associated with UV-sensitive cones. DNA sequencing shows that lacertids have a functional SWS1 opsin, very similar at 13 critical sites to that in the presumed ancestral vertebrate (which was UV sensitive) and other UV-sensitive lizards. Finally, males of Podarcis muralis are capable of discriminating between two views of the same stimulus that differ only in the presence/absence of UV radiance. Taken together, these results provide convergent evidence of UV vision in lacertids, very likely by means of an independent photopigment. Moreover, the presence of four oil droplet types suggests that lacertids have a four-cone colour vision system.

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Section: Discussionmentioning

confidence: 99%

Ultraviolet vision in lacertid lizards: evidence from retinal structure, eye transmittance, SWS1 visual pigment genes, and behaviour

Lanuza

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2014

Journal of Experimental Biology

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“…Given the fact that diurnal geckoes are foveated while nocturnal geckoes are not, the superficial fovea of crocodilians may represent a halfway point between the two that reflects their arrhythmic lifestyle (Röll, 2001;Barbour et al, 2002). Alternatively, the similar ratio of eye size and SRP described above for crocodile juveniles and nocturnal geckoes may suggest that the crocodilian fovea is vestigial.…”

Section: Specialised Distribution Of Retinal Ganglion Cells and Its Rmentioning

confidence: 99%

“…The very narrow and superficial fovea in the vertical centre of the streak implies less lateral displacement of retinal ganglion cells than what occurs in the fovea of diurnal lizards (Chievitz, 1889;Laurens and Detwiler, 1921;Röll, 2001;Barbour et al, 2002). Given the fact that diurnal geckoes are foveated while nocturnal geckoes are not, the superficial fovea of crocodilians may represent a halfway point between the two that reflects their arrhythmic lifestyle (Röll, 2001;Barbour et al, 2002).…”

Section: Specialised Distribution Of Retinal Ganglion Cells and Its Rmentioning

confidence: 99%

“…The shape and position of retinal regions of high ganglion cell density have been correlated with the visual environment and lifestyle of many animal groups, including reptiles, birds and mammals (Hughes, 1977;Barbour et al, 2002;Coimbra et al, 2009). Both saltwater and freshwater crocodiles spend a significant proportion of their time waiting for the right time to ambush prey in a 'minimum exposure' posture with only the eyes and nostrils protruding above the water's surface.…”

Section: Introductionmentioning

confidence: 99%

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Spatial resolving power and spectral sensitivity of the saltwater crocodile, Crocodylus porosus, and the freshwater crocodile, Crocodylus johnstoni

Nagloo

Collin

Hemmi

et al. 2016

Journal of Experimental Biology

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Crocodilians are apex amphibious predators that occupy a range of tropical habitats. In this study, we examined whether their semiaquatic 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, 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 λ max ), green (502/510 nm λ max ) and red (546/ 554 nm λ max ) sensitive, indicating the potential for trichromatic colour vision. The visual pigments of both members of the twin cones have the same λ max as the red-sensitive single cone and the rod has a λ max at 503/510 nm (saltwater/freshwater). The λ max 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.

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“…All Iguania thus far studied show the same basic pattern of retinal photoreceptors. All appear to have tetrachromatic colour vision based on four classes of cone pigments with similar peak absorption wavelengths (l max ) [7,8,27,28]. Among the Gekotta, both nocturnal and diurnal forms have only three classes of photoreceptors (referred to as rods in the nocturnal forms, and cones in the diurnal).…”

Section: Introductionmentioning

confidence: 99%

High sensitivity to short wavelengths in a lizard and implications for understanding the evolution of visual systems in lizards

2011

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Progress in developing animal communication theory is frequently constrained by a poor understanding of sensory systems. For example, while lizards have been the focus of numerous studies in visual signalling, we only have data on the spectral sensitivities of a few species clustered in two major clades (Iguania and Gekkota). Using electroretinography and microspectrophotometry, we studied the visual system of the cordylid lizard Platysaurus broadleyi because it represents an unstudied clade (Scinciformata) with respect to visual systems and because UV signals feature prominently in its social behaviour. The retina possessed four classes of single and one class of double cones. Sensitivity in the ultraviolet region (UV) was approximately three times higher than previously reported for other lizards. We found more colourless oil droplets (associated with UV-sensitive (UVS) and short wavelength-sensitive (SWS) photoreceptors), suggesting that the increased sensitivity was owing to the presence of more UVS photoreceptors. Using the Vorobyev -Osorio colour discrimination model, we demonstrated that an increase in the number of UVS photoreceptors significantly enhances a lizard's ability to discriminate conspecific male throat colours. Visual systems in diurnal lizards appear to be broadly conserved, but data from additional clades are needed to confirm this.

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Retinal characteristics of the ornate dragon lizard, Ctenophorus ornatus

Cited by 69 publications

References 57 publications

Ultraviolet vision in lacertid lizards: evidence from retinal structure, eye transmittance, SWS1 visual pigment genes, and behaviour

Ultraviolet vision in lacertid lizards: evidence from retinal structure, eye transmittance, SWS1 visual pigment genes, and behaviour

Spatial resolving power and spectral sensitivity of the saltwater crocodile, Crocodylus porosus, and the freshwater crocodile, Crocodylus johnstoni

High sensitivity to short wavelengths in a lizard and implications for understanding the evolution of visual systems in lizards

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