The fish eye view: are cichlids conspicuous
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2010-06-11
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Brian E. Dalton, Thomas W. Cronin, N. Justin Marshall, Karen L. Carleton, The fish eye view: are cichlids conspicuous? , Journal of Experimental Biology 2010, 213: 2243-2255; doi: 10.1242/jeb.037671
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Abstract
The extent of animal colouration is determined by an interplay between natural and sexual selection. Both forces probably shape
colouration in the speciose, rock-dwelling cichlids of Lake Malawi. Sexual selection is thought to drive male colouration,
overcoming natural selection to create conspicuous colour patterns via female mate choice and male–male competition. However,
natural selection should make female cichlids cryptic because they mouthbrood their young. We hypothesize that as a result of
both sexual and natural selection, males will have colours that are more conspicuous than female colours. Cichlid spectral
sensitivity, especially in the ultraviolet, probably influences how colours appear to them. Here we use simple models of the
trichromatic colour space of cichlid visual systems to compare the conspicuousness of male and female nuptial colours of nine
species. Conspicuousness of colours was evaluated as their Euclidian distance in colour space from environmental backgrounds
and from other colours on the same fish. We find in six of the nine species that breeding males have colours that are statistically
more conspicuous than female colours. These colours contrast strongly with each other or with the backgrounds, and they fall
within a range of spectra best transmitted in the habitat. Female colour distances were sometimes smaller, suggesting that
females of some species are more cryptic than males. Therefore, selection can differentially act to generate male colours that are
more conspicuous than those in females. However, in two species, females had colours that were more conspicuous than male
colours, suggesting that other selective forces and possibly sexual conflicts are acting in this system.