Colour vision and visual ecology of the blue-spotted maskray, Dasyatis kuhlii Müller & Henle, 1814

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.

How does the blue-ringed octopus (Hapalochlaena lunulata) flash its blue rings?

“…The peak reflectance of the blue ring lies well within the range of mid-and long-wavelength sensitive opsins of potential marine vertebrate and invertebrate predators, including cetaceans, pinnipeds, birds, teleost fishes and other cephalopods (Hanlon and Messenger, 1996;Cronin et al, 2000;Hart, 2004;Levenson et al, 2006;Gacic et al, 2007;Theiss et al, 2007). Furthermore, the blue-green part of the visible spectrum is the most prominent ambient underwater light field (Tyler and Smith, 1970;Jerlov, 1976), so the iridescence is spectrally well tuned to be maximally visible.…”

Behavioural evidence for colour vision in an elasmobranch

“…Moreover, colour-opponent responses were recorded from horizontal cells in the retina of the red stingray, Dasyatis akajei (Toyoda et al, 1978), and recent MSP studies have reported the presence of up to three spectrally distinct cone types in three ray species, including G. typus (Hart et al, 2004;Theiss et al, 2007). The results obtained from the present study suggest that G. typus, and most likely other rays with multiple cone types, are capable of discriminating a coloured reward stimulus from a range of different coloured distracter stimuli of varying brightness.…”

“…The evidence for more than one spectral cone type in the ray retina, however, is more convincing, with studies indicating the presence of more than one photopic cone-based mechanism (Govardovskii and Lychakov, 1977;Toyoda et al, 1978). Recently, data obtained using MSP have indicated the presence of up to three spectrally distinct cone pigments in the retina of the giant shovelnose ray, Glaucostegus typus [wavelength of maximum absorbance ( max )477, 502 and 561nm], the eastern shovelnose ray, Aptychotrema rostrata ( max 459, 492 and 553nm) (Hart et al, 2004), and the bluespotted maskray, Neotrygon (Dasyatis) kuhlii ( max 476, 498 and 552nm) (Theiss et al, 2007). These findings raise the possibility that rays have a potentially trichromatic colour vision system.…”

Visual optics and ecomorphology of the growing shark eye: a comparison between deep and shallow water species

“…LCA is greatest for short wavelengths of light (blue-ultraviolet), so it is possible that LCA may occur at wavelengths below the spectral range investigated in this study. Short wavelength image defocus would, however, be somewhat controlled by the transmission properties of the ocular media, which are opaque to wavelengths below 400nm (juvenile and adult S. mitsukurii) and below 310nm and 382nm for juvenile (65cm TL) and adult (142cm TL) C. plumbeus, respectively (Fig.5).Short wavelength-filtering ocular media, as shown in S. mitsukurii (Fig.5) , have been found in other elasmobranch species including the wobbegong shark Orectolobus ornatus (T 50 403nm) (Siebeck and Marshall, 2001), the grey reef shark, C. amblyrhynchos (T 50 400nm) , and several batoid species (T 50 402-437nm) (Siebeck and Marshall, 2001;Theiss et al, 2007). The light-filtering properties of the ocular media are attributed to a group of UV-absorbing pigments called mycosporinelike amino acids (MAAs), one of which, asterina-330, has been identified in shark lenses (Dunlap et al, 1989;Douglas and Marshall, 1999).…”