Losses of functional opsin genes, short-wavelength cone photopigments, and color vision—A significant trend in the evolution of mammalian vision

All mammalian cone photopigments are derived from the operation of representatives from two opsin gene families (SWS1 and LWS in marsupial and eutherian mammals; SWS2 and LWS in monotremes), a process that produces cone pigments with respective peak sensitivities in the short and middle-to-long wave...

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Published in:Visual neuroscience Vol. 30; no. 1-2; pp. 39 - 53
Main Author: JACOBS, GERALD H.
Format: Journal Article
Language:English
Published: New York, USA Cambridge University Press 01.03.2013
Subjects:
Animals
Biological Evolution
Color Perception - genetics
Evolution
Genes
Genetics
Humans
Mammals
Opsins - classification
Opsins - genetics
Phylogeny
Pigments
Primates
Retinal Cone Photoreceptor Cells - physiology
Review Article
Vision Disorders - genetics
Vision, Ocular - genetics
Eutherian evolution
SWS1 opsin genes
Pseudogenes
Mammalian color vision
Cone pigments
Visual adaptations
ISSN:0952-5238, 1469-8714, 1469-8714
Online Access:Get full text
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Summary:All mammalian cone photopigments are derived from the operation of representatives from two opsin gene families (SWS1 and LWS in marsupial and eutherian mammals; SWS2 and LWS in monotremes), a process that produces cone pigments with respective peak sensitivities in the short and middle-to-long wavelengths. With the exception of a number of primate taxa, the modal pattern for mammals is to have two types of cone photopigment, one drawn from each of the gene families. In recent years, it has been discovered that the SWS1 opsin genes of a widely divergent collection of eutherian mammals have accumulated mutational changes that render them nonfunctional. This alteration reduces the retinal complements of these species to a single cone type, thus rendering ordinary color vision impossible. At present, several dozen species from five mammalian orders have been identified as falling into this category, but the total number of mammalian species that have lost short-wavelength cones in this way is certain to be much larger, perhaps reaching as high as 10% of all species. A number of circumstances that might be used to explain this widespread cone loss can be identified. Among these, the single consistent fact is that the species so affected are nocturnal or, if they are not technically nocturnal, they at least feature retinal organizations that are typically associated with that lifestyle. At the same time, however, there are many nocturnal mammals that retain functional short-wavelength cones. Nocturnality thus appears to set the stage for loss of functional SWS1 opsin genes in mammals, but it cannot be the sole circumstance.
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ISSN:0952-5238
1469-8714
1469-8714
DOI:10.1017/S0952523812000429