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BMC Biology

, 8:133

First Online: 28 October 2010Received: 14 July 2010Accepted: 28 October 2010


BackgroundColor vision plays a critical role in visual behavior. An animal-s capacity for color vision rests on the presence of differentially sensitive cone photoreceptors. Spectral sensitivity is a measure of the visual responsiveness of these cones at different light wavelengths. Four classes of cone pigments have been identified in vertebrates, but in teleost fishes, opsin genes have undergone gene duplication events and thus can produce a larger number of spectrally distinct cone pigments. In this study, we examine the question of large-scale variation in color vision with respect to individual, sex and species that may result from differential expression of cone pigments. Cichlid fishes are an excellent model system for examining variation in spectral sensitivity because they have seven distinct cone opsin genes that are differentially expressed.

ResultsTo examine the variation in the number of cones that participate in cichlid spectral sensitivity, we used whole organism electrophysiology, opsin gene expression and empirical modeling. Examination of over 100 spectral sensitivity curves from 34 individuals of three species revealed that 1 spectral sensitivity of individual cichlids was based on different subsets of four or five cone pigments, 2 spectral sensitivity was shaped by multiple cone interactions and 3 spectral sensitivity differed between species and correlated with foraging mode and the spectral reflectance of conspecifics. Our data also suggest that there may be significant differences in opsin gene expression between the sexes.

ConclusionsOur study describes complex opponent and nonopponent cone interactions that represent the requisite neural processing for color vision. We present the first comprehensive evidence for pentachromatic color vision in vertebrates, which offers the potential for extraordinary spectral discrimination capabilities. We show that opsin gene expression in cichlids, and possibly also spectral sensitivity, may be sex-dependent. We argue that females and males sample their visual environment differently, providing a neural basis for sexually dimorphic visual behaviour. The diversification of spectral sensitivity likely contributes to sensory adaptations that enhance the contrast of transparent prey and the detection of optical signals from conspecifics, suggesting a role for both natural and sexual selection in tuning color vision.

AbbreviationsCCDcharge-coupled device

Dim-SWdim short-wavelength-isolation background condition


FWHMfull width half max

GnRHGonadotropin-releasing hormone

SWshort-wavelength-isolation background condition

LWlong-wavelength-isolation background condition

LWSlong wavelength sensitive

MCMmultiple-cone mechanism

NAnumerical aperture

NISTNational Institute of standards and technology

ODoptical density


RIresponse versus intensity

SWSshort wavelength sensitive

THthyroid hormones


Electronic supplementary materialThe online version of this article doi:10.1186-1741-7007-8-133 contains supplementary material, which is available to authorized users.

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Autor: Shai Sabbah - Raico Lamela Laria - Suzanne M Gray - Craig W Hawryshyn


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