Hormone-Induced Masculinization in Xiphophorus helleri: Comparative Effects of Immersion and Dietary 17α-Methyltestosterone Treatments

The present study evaluated the effects of different doses of 17α-methyltestosterone (17α-MT) administered through immersion and supplementary diet on sex reversal and survival in Xiphophorus helleri (Red Swordtail). Hatchlings were exposed to six hormone concentrations (0, 100, 200, 300, 400, 500, and 600 μg/L) for 6 hours and reared for 90 days. Sex ratio, intersex incidence, and survival were recorded. Results showed a progressive increase in male proportion with increasing hormone concentration in both immersion and diet treatments. The highest male ratio (0.90 and 0.85**, respectively) occurred at 500–600 μg/L treatments, with minimal intersex development (0.02–0.05). The control group exhibited a balanced sex ratio (0.50 male: 0.50 female). Survival remained uniformly high (100%) across all treatments. Microscopic examination of gonadal tissues revealed clear differentiation between ovarian oocytes and testicular spermatocytes in hormone-treated groups, confirming effective masculinization. These findings indicate that 17α-MT is highly effective in producing monosex male populations of X. helleri with negligible mortality, making it suitable for ornamental fish production. These results provide valuable insights for hormone-based sex manipulation strategies in livebearer aquaculture, particularly for all-male production systems aimed at improving uniformity and economic returns.