The Control of Bright Colored Pigment Cells of Fishes and Amphibians

SYNOPSIS. The bright colored pigment cells of fishes and amphibiansinclude xanthophores, erythrophores, and iridophores. Theirultrastructure and pigmentary composition are discussed. Therole of the hypophysis in controlling both physiological andmorphological changes of color in both groups is discussed.The nervous system may be involved in physiological responsesof fish iridophores. The physiology of the amphibian iridophoreis discussed from the point of view of its parallelism of responseto that of the melanophore. Intermedin causes iridophores tocontract as do several drugs; the effect of intermedin can bereversed by still other agents. Melatonin has no effect on iridophores.Xanthophores of some fishes and amphibians are induced to expandby intermedin. The morphological effects of intermedin at theorganellar level are presented in terms of ultrastructure andpigmentary composition. The integrated response of amphibiandermal chromatophores to intermedin is described as a basicmechanism for change in color.