Chromatophore development and cell interactions in the skin of xiphophorine fish.

Regeneration-induced development of chromatophores in the skin of fish was used to study cell interactions affecting cell differentiation and cell destruction. The typical differentiation process of chromatophores in the regenerating fish skin is described with special interest in the differentiation of macro- and micromelanophores. Between micro- and macromelanophores two types of cell interactions were found: 1. The macromelanophores inhibit the differentiation of melanocytes and micromelanophores 2. the macromelanophores induce the destruction of micromelanophores in their vicinity. These cell interactions are very specific to cell type, that means they are strictly limited to macro- and micromelanophores. On the other hand, the effectiveness of these cell interactions isnot limited to one genotype or one species of Xiphophorine fish. The inhibiting and the destruction-inducing influence of macromelanophores upon micromelanophores is shown for three different species of Xiphophorine fish. The role of cell interaction in chromatophore development is discussed.