Production of XX neo-male mandarin fish, Siniperca chuatsi, after sexual differentiation by oral administration of 17-methyltestosterone

A well-known fact about mandarin fish (Siniperca chuatsi) is that females grow faster than males. Mandarin fish that have all-female populations have economic advantages, but traditional neo-male fish are difficult to produce. In this study, indirect feeding of 500 mg/kg 17 alpha-methyltestosterone (MT) to XX mandarin fish (60 dpf, days post fertilization) with completely differentiated ovaries induced secondary sex reversal. At 40 days after MT treatment, 14.7% of mandarin fish with complete reversal was produced, which showed for the first time that XX mandarin fishes with differentiated ovaries still have potentially bisexual germ cells and the plasticity of sex reversal. In the MT treatment group, there was no significant difference in survival compared to the control group. The body weight of the MT treatment group was significantly lower than that of the control group 40 days after treatment (dat) (P < 0.05). During MT treatment, serum 11-KT and T concentrations increased and serum E2 concentration decreased in the MT treatment group, but there was no significant difference in hormone levels between the MT treatment group and the control group. A masculinization of mandarin fish was also confirmed by the expression patterns of sex-specific genes sox9, dmrt1, cyp19a1a and foxl2. A significant amount of sox9 and dmrt1 was expressed in the fish gonads of the MT treatment group, whereas cyp19a1a and foxl2 were minimally expressed in the fish gonads.