Effects of 17α-Methyltestosterone Immersion Treatments on Sex Reversal of Mud Loach, Misgurnus mizolepis

Abstract

Effects of 17α-methyltestosterone (MT) immersion treatments at selected doses and durations on sex reversal of the mud loach Misgurnus mizolepis were examined. Fry were immersed in water containing MT 0, 25, 50, 100 or 200 μg per l for one, two or three weeks. Survival decreased as dose and treatment duration increased; in most instances it was significantly lower than that of the controls (p < 0.05). Growth rate at all the treatment combinations did not differ, when compared to that of control (p > 0.05). The treatment with 200 μg MT l-1 for two or three weeks produced all male populations, and the group treated with 100 μg l-1 for three weeks also became nearly an all male population (99.3%). The morphological and histological attributes of testes of the hormone-treated fish were similar to those of normal males. The hormone treatment altered the secondary sexual character of the fish, namely the size and morphology of the pectoral fins.