Xanthophores in Fundulus, with Special Consideration of Their “Expanded” and “Contracted” Phases

Abstract

Demonstration of the actual forms of the "expanded" and the "contracted" dermal xanthophore in F. heteroclitus L. has been afforded through the fixation and clearing of tissues in Stockard''s solution followed by Brunn''s glucose medium. Small scales from the dorsal or caudal regions of yellow-adapted and dark-adapted fishes prepared in this manner revealed many yellow cells in clear definite outline. Prolonged staining with dilute methyl green aided greatly in the determination of the form and location of the nuclei. The xanthophore appeared as a small flat cell with many long ameboid processes, exhibiting relative constancy of form in each of its phases. In the "expanded" condition, yellow lipochrome pigment was observed in uniform distribution throughout the cell. The "contracted" phase, however, showed a compact aggregation of this pigment in a central area, while the form of the cell and its general outline remained essentially unchanged. The structure of the xanthophore, therefore, agrees essentially with that of the melanophore.