Cellular Aspects of the Control of Physiological Color Changes in Fishes

SYNOPSIS. Recent advances in the cellular aspects of chromatophoricactivities in fishes are reviewed, special emphasis being laidon the black pigment-containing cells, the melanophores. A fewrecent electron-microscopic studies have disclosed the finestructure of melanophores. They are enclosed with a single cellmembrane, within which melanosomes and other cell organellesare found. All observations favor the view that melanosomesare selectively moved through the cellular processes, leavingthe cell contour rather fixed. In regard to these findings,current ideas about the mechanisms of pigment movements arediscussed. Particular attention is directed to the possibleintervention of microtubules and the theory of migration ofpigment by intracellular electrophoresis. The regulatory mechanismsof pigment cells are then dealt with. The adrenergic natureof transmission is affirmed in the peripheral melanin-aggregatingnervous system. The mode of nervous supply to a melanophoreis also analyzed. Investigations of the antagonistic, melanin—dispersing,nervous system are also considered, with special reference torecent physiological studies and to the finding of synapticvesicles by electron microscopy. On the basis of these results,a new interpretation of the so-called Parker effect is proposed.