Endocrine Regulation of Pigmentation in Fish

Abstract

This article reviews the development of knowledge of physiological and morphological color change in fishes. Emphasis is placed on research in the last three years. Although direct evidence may not be available at present, an attempt is made to show a unifying theme. It is apparent that those circumstances that lead to pigment dispersion as a physiological color change also favor the development of a dark morphological color and vice versa for pigment aggregation. There is ample evidence that control of color change in fishes ranges from fully nervous to fully hormonal. It may be that both neural and endocrine agents exert their effects upon the melanophore by causing changes in the amount of cyclic AMP in the cell. Rhythmic color change, which appears to be a special instance of physiological color change is discussed, but no conclusions are drawn. A tentative scheme for the unification of physiological and morphological color change is advanced with the note that direct evidence is not currently available to support all of it.