Pigments of a color polymorphism in a cichlid fish.

i. Cichlasoma citrinellum occurs as gray or gold morphs in lakes in Nicaragua. The gold morph is variable and individuals range from yellow to dark orange. 2. The pigments responsible for the carotenoid coloration are E-carotene and canthaxanthin. The gray morph contains a carotenoid component and also heavy melanin deposits. 3. The carotenoids are dietary in origin, but their distribution and intensity is presumably under genetic control. 4. The relation of color morphs to the ecological and selective forces which might produce them is discussed.