Cichlids [pronounced sik-lids] have several different cone opsin genes that enable them to detect light across the visible and ultraviolet regions of the spectrum. Different species express different subsets of these opsins to create alternate visual systems. Recent research has shown that cichlid fish in the clear waters of Lake Malawi expressed a wide range of opsins, with closely related species differing in whether they used the shorter wavelength or longer wavelength gene combinations.
PLoS Biology article: "The Eyes Have It: Regulatory and Structural Changes Both Underlie Cichlid Visual Pigment Diversity" by Christopher M. Hofmann, Kelly E. O'Quin, N. Justin Marshall, Thomas W. Cronin, Ole Seehausen4,5, Karen L. Carleton. (Not just another fish story)
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