The gonadotropic cells in the pituitary of the black molly, Mollienisia latipinna, and other teleosts, identified by the immunofluorescence technique in normal and androgen-treated animals.

Using anti-carp-gonadotropic-gamma-globulin, the indirect immunofluorescence technique was applied to sections of the pituitary of 12 teleost species. From the investigated species, the Poeciliinae, and especially the black molly, showed a distinct localization of fluorescent cells in the mesoadenohypophysis. Strong fluorescence was observed in the ventralmost region, containing the presumed gonadotropic cells; weak fluorescence was observed in the dorsal region, in the presumed thyrotropic cells. The possibility of an unspecific reaction with TSH-cells in the latter region is discussed. Treatment of male black mollies for 38 days with methyltestosterone resulted in a loss of fluorescence in the ventral region of the meso-adenohypophysis, whereas there was no decrease of the fluorescence in the dorsal region. The results support the hypothesis that the ventral basophils in the mesoadenohypophysis produce gonadotropic hormone.