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Vision in sharks and rays: Opsin diversity and colour vision
1Department of Biological Sciences, Macquarie University, NSW, 2109, Australia.
Seminars in Cell & Developmental Biology
|April 26, 2020
Summary
Sharks are cone monochromats, lacking color vision, unlike most rays which are dichromats. This suggests sharks may have lost color vision multiple times, prompting a reevaluation of its marine benefits.
Area of Science:
- Comparative vision research
- Elasmobranch biology
- Evolutionary adaptations
Background:
- Elasmobranch (sharks and rays) visual systems are less understood than teleost (bony fish) vision.
- Elasmobranch eyes possess unique specializations contributing to their evolutionary success.
- Understanding visual pigments is key to elasmobranch diversification.
Purpose of the Study:
- To review recent findings on visual pigments in sharks and rays.
- To examine the phylogenetic distribution of these visual pigments.
- To reassess the adaptive significance of color vision in marine predators.
Main Methods:
- Review of existing literature on elasmobranch visual pigments.
- Analysis of phylogenetic data on visual pigment distribution.
- Comparative analysis with other marine predator visual systems.
Main Results:
- Most rays are cone dichromats, possessing two types of cone photoreceptors.
- All studied sharks are cone monochromats, possessing only one type of cone photoreceptor.
- Sharks appear to have independently lost color vision on multiple occasions.
Conclusions:
- Elasmobranchs exhibit diverse visual pigment compositions, with significant differences between sharks and rays.
- The monochromatic vision in sharks parallels that of other marine predators like pinnipeds and cetaceans.
- The study necessitates a re-evaluation of the evolutionary costs and benefits of multiple cone pigments and wavelength discrimination in marine environments.
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