Optimization of neo-female induction by 17β-estradiol administration and subsequent production of YY males in yellow drum (Nibea albiflora)

Yellow drum (Nibea albiflora) is an economically important mariculture species in China, and males are particularly favored by consumers due to their slender body shape. This study aimed to produce neo-females (females with XY genotype) through sex reversal and subsequently generate YY males. Yellow drum fry (30 days post-hatching, dph) was fed with pellets containing 1, 5, or 10 mg/kg of 17β-estradiol (E2) for 60 days to induce sex reversal. Treatments with 5 and 10 mg/kg E2 resulted in feminization of all 17 genetic males examined, whereas the 1 mg/kg group achieved only 55.6% sex reversal (5 out of 9 genetic males). At the end of the treatments, mean body weights in the 5 and 10 mg/kg groups were 25.29% and 30.58% lower than that of the control group, respectively, exhibiting a clear dose-dependent effect. Based on these results, the 5 mg/kg dosage appears sufficient for effective neo-female induction. Gene expression analysis showed substantially higher cyp19a1a expression in neo-females than in male and female controls at 180, 270, and 360 dph while dmrt1 expression remained consistently lower than in controls at all three time points, suggesting stimulation of E2 synthesis and inhibition of dmrt1 expression under the effect of exogenous E2 persisted long after treatments ended. Notably, YY males were identified among the offspring of neo-females crossed with normal males using molecular sexing, and these YY males exhibited gonadal development similar to that of XY males at 90 dph. This study establishes an effective approach for neo-female induction and YY male production in yellow drum.