Efficacy of 17 α-methyl testosterone and letrozole on sex reversal of protogynous grouper,Epinephelus tauvina(Forskal, 1775) and spawning performance of sex-reversed males

This study aimed to test the efficacy of 17 α-methyl testosterone (17 α-MT) alone and in combination with letrozole, an aromatase inhibitor, for the induction of sex reversal in protogynous greasy grouper, Epinephelus tauvina. Further, the long-lasting effects of these treatments and spawning performance of sex-reversed males were also investigated. Greasy grouper with oocytes in the perinucleolus stage were implanted with 5 mg 17 α-MT kg−1 body weight (T1), 5 mg 17 α-MT and 0.2 mg letrozole kg−1 body weight (T2) and 5 mg 17 α-MT with 0.4 mg letrozole kg−1 body weight (T3) and no androgens/enzyme inhibitor implanted (C). The 17 α-MT alone and in combination of letrozole-induced sex reversal in greasy grouper, whereas untreated control fish (C) showed normal ovarian development. However, T2 and T3 group showed 100% sex reversal and completion of spermatogenesis up to functional male phase in 2 and 3 months, respectively, whereas T1 group resulted in only 66.67% functional male with motile spermatozoa after 4 months. Sex-reversed males successfully fertilized the eggs during induced spawning. There were significant differences on fertilization and hatching rates between T2 group (79.00 ± 4.36%; 77.67 ± 2.87%, respectively) and T1 group (57.67 ± 3.17%; 63.87 ± 2.91%, respectively). The result suggested that 17 α-MT (5.0 mg kg−1 BW) in combination with letrozole (0.2 mg kg−1 BW) has the potential to produce 100% sex-reversed male in short period in greasy grouper, which might greatly help in seed production of greasy grouper.