Ultrastructural comparisons were made of cutaneous pigment cells from analogous skin areas of variant albinistic and control wild-type bullfrogs, Rana catesbeiana. In the epidermis, the wild-type melanocytes contained numerous mature melanosomes whereas the albinistic epidermal melanocytes demonstrated retarded melanogenesis with premelanosome stages dominant. In the dermal chromatophore unit of both frogs, no morphological differences were observed in the xanthophores, but significant morphological distinctions were noted in the melanophores and iridophores. The wild-type dermal melanophores contained numerous mature melanosomes whereas the albinistic dermal melanophore demonstrated retarded melanogenesis similar to that found in its epidermal melanocyte. The albinistic iridophores not only had reduced reflecting platelet areas, but also the platelets were aberrant in morphology compared to the rectangular shape of the reflecting platelets in the wild type. The mutant reflecting platelets were small, spherical, and highly irregular in shape. It is suggested that the development of each type of albinistic melanocyte, melanophore, and iridophore might occur if defective MSH-membrane-receptors altered or diminished the cell response to MSH during pigment cell ontogeny.
ASJC Scopus subject areas
- Molecular Biology