ommochrome, any of a group of biological pigments (biochromes) conspicuous in the eyes of insects and crustaceans as well as in the changeable chromatophores (pigment-containing cells) in the skin of cephalopods. Ommochromes are derived from the breakdown of the amino acid tryptophan.
Ommochromes, although responsible for the colors of insect eyes, are not known to be involved directly in photoreception. Rather, in insects and cephalopods, the pigments appear to offer some protection against oxidative stress. In insect eyes, for example, ommochromes have been found to inhibit peroxidation reactions induced by visible light in photoreceptor cells. In the changing integumentary cells of cephalopods, they may further contribute to adaptive responses.