Mitotic activity of differentiated goldfish erythrophores in culture.

Integumental erythrophores on the scales of xanthic goldfishes were dissociated and cultured in a monolayer for about 30 days. The proportion of erythrophores in the culture was about 50% at the beginning of cultivation. Erythrophores in culture were characterized by the aggregate of orange-coloured pigment in the centre of the cell body. With the progress of culture the erythrophores develop a few elongated dendritic processes and came to rest on a monolayer sheet of coexisting non-pigmented cells. The erythrophores responded to adrenocorticotropic hormone (ACTH) by producing reversible pigment dispersion and this response was retained throughout the whole period of culture. Dividing erythrophores were found first within 3 days of cultivation and at all times after that. The number of the erythrophores doubled within 9 days of cultivation and trebled within 16 days. Thus, evidence was provided that differentiated erythrophores of the goldfish still showed mitotic activity in vitro, in contrast to the generally accepted view that fish chromatophores are kind of terminally differentiated cell.