Masculinization of fighting fish, Betta splendens Regan, using synthetic or natural androgens

Abstract

The effects of two synthetic androgens, 17α-methyltestosterone (5-50mg/kg food), 19-nor-ethynyltestosterone (2-50 mg/kg food) and two natural androgens, 11 ketotestosterone (10-60mg/kg food) and androstenedione (20-100mg/kg food) were investigated in the fighting fish, Betta splendens Regan. Androgens were administered for 40 days from the first day of feeding. Masculinization occurred in 100% of individuals fed 8, 15, 60, 90 mg/kg food 19-nor-ET, 17α-MT, 11-KT and AT respectively. Mortality due to treatment of natural steroids was significantly less than that with the synthetic steroids. Sex-reversed males were sexually functional and their genotype was identified by progeny testing. Sex-reversed males produced 100% female monosex when mated with normal females, indicating that the mechanism of sex determination in this fish is homogametic female and heterogametic male.