Effects of Busulfan on Serum Steroid Hormones, GSI, Gonad Development and Sex Reversal in the Asian Swamp Eel (Monoptrus Albus)

This study investigated the effects of busulfan on sex reversal in the Asian swamp eel (Monopterus albus) by evaluating the estradiol (E2) and testosterone (T) concentrations, gonadosomatic index (GSI) and sex ratio. Fish (9.80 ± 1.07 g average initial weight; n = 3 per group) were fed with five diets containing 0 (control), 10, 30, 50 or 70 mg kg-1 dietary busulfan concentrations to apparent satiation for 15 months. Serum E2 and T concentrations were determined by radioimmunoassay techniques. Both E2 and T concentrations were significantly affected by busulfan, while there were no significant differences among the treated groups. Serum E2 concentrations and GSIs decreased, while T concentrations increased with increasing busulfan levels in each group. A shift in the sex ratio towards more male and intersex fish was observed with increasing busulfan contents. The highest male ratio obtained in the 70 mg kg-1 group was significantly different compared to the other groups. High doses of busulfan may induce deformed individuals and high mortality in M. albus. Therefore, busulfan may inhibit gonad development and promote the sex change from female to male M. albus.