Artificial induction of female-to-male sex change in the leopard coral grouper Plectropomus leopardus via intraperitoneal administration of 17α-methyltestosterone and letrozole

The leopard coral grouper Plectropomus leopardus is in high demand, and a stable supply of aquaculture broodstock is necessary. However, since this species is a protogynous hermaphrodite, production of male broodstock is time-consuming. In this study, we investigated the effect of intraperitoneal administration of 17 alpha-methyltestosterone (MT) and letrozole (LZ) on gonadal sex change and steroidogenesis in adult female P. leopardus. The fish were divided into seven groups: two MT silicon tube implant groups (1 and 5 mg/kg), two LZ cacao butter implant groups (1 and 5 mg/kg/month), one group implanted with both MT (5 mg/kg) and LZ (5 mg/kg/month), and two control groups (one vehicle-only, and the other intact). Silicon tube implants were inserted at the start of treatment, and cacao butter implants were injected at the start and monthly for 3 months. After treatment, the MT group showed an incomplete sex change with a decrease in estradiol-17 beta (E2), while the LZ groups completed their sex change with decreased E2 and increased 11-ketotestosterone (11-KT). The MT + LZ group also completed sex change with decreased E2, but only a trend toward increased 11-KT. These results indicate that LZ administration was effective for inducing female-to-male sex change in adult P. leopardus.