The Degree of Differentiation in Early‐ and Late‐onset Forms of Platyfish‐swordtail Hybrid Melanomas: A Morphological and Physiological Study in Primary Culture

Abstract

The early- and late-onset forms of platyfish-swordtail hybrid melanomas (fry and adult melanomas) and the macromelanophores of platyfish and melanotic hybrids were cultured and characterized according to their cellular morphology and physiology. The fry melanomas contained many large and broad cells. The pigmentation of these cells was somewhat less than that of the macromelanophores of platyfish. Most of the fry melanoma cells responded rapidly to 10-6M epinephrine, exhibiting reversible melanosome aggregation. The adult melanomas consisted of small, dendritic and sparsely pigmented cells. The physiological response of these adult melanoma cells varied widely from tumor to tumor. These findings are discussed in relation to the differentiation of fish melanophores.