Formation of Melanin in Regenerating Limbs of a Crustacean

Abstract

THE pigmentation of the isopod crustacean Asellus aquaticus is chiefly due to a melanin¹ distributed in granular form in the cytoplasm of stellate cells of the usual arthropod-type, underlying and interpenetrating² the epidermal cells. The newly eclosed regenerating limb is macroscopically unpigmented, and is very conspicuous. Microscopically, incipient pigmentation is sometimes visible, and otherwise becomes evident in a day or two, as golden-brown granules, in the cytoplasm of large wandering cells (17 µ or larger), at the time when these presumptive pigment cells first begin to assume their definitive position, and their asteroid form. These large wandering cells are a conspicuous feature of the newly eclosed limb, and decrease in number as pigmentation progressively develops, during the stadium following eclosion.