The differentiation of leaf frog melanophores in culture.

During early larval development of mexican leaf frog, Pachymedusa dacnicolor, dermal melanophores are typically black, but a few brown melanophores appear about stage 18. During metamorphic climax brown melanophores begin to dominate and by stage 23 they are the exclusive type. The synthesis of the pigment, a red pteridine-dimer, occurred in the melanophores of organ-cultured back skin isolated from tadpoles. The development of this pigmentation in organ culture was independent of thyroxine at least after the onset of metamorphic climax (stage 19). Isolated melanophores in cell culture conditions proliferated only in the presence of MSH, but even these proliferating melanophores, if derived from larvae of stage 21 or younger, showed no indication of pterorhodin synthesis. Melanophores derived from a stage 22 larva and cultured for 18 days synthesized and deposited pterorhodin.