Effect of hormone treatments on alarm substance cell counts in the pearl dace, Semotilus margarita

Abstract

The seasonal loss of alarm substance cells that normally occurs in breeding male and female pearl dace, Semotilus margarita, could not be induced by treatment with androgen, estrogen, salmon gonadotropin, or prolactin. Treatment with carp pituitary did lead to a significant reduction in alarm substance cell numbers. Androgen treatment induced changes in tuberculation and mucous cell counts. Salmon gonadotropin and carp pituitary increased breeding colouration. Prolactin treatment increased mucous cell counts. The lack of response of pearl dace alarm substance cells to androgen contrasts with the situation in fathead minnows, Pimephales promelas, where seasonal alarm substance cell loss is under androgen control. The difference may reflect differences in the annual cycle of secondary sexual characteristics.