Effects of estradiol-17β on survival, growth performance, sex reversal and gonadal structure of bluegill sunfish Lepomis macrochirus
2008
Wang, Han-Ping | Gao, Zexia | Beres, Beatrix | Ottobre, Joseph | Wallat, Geoff | Tiu, Laura | Rapp, Dean | O'Bryant, Paul | Yao, Hong
We systematically investigated the feminization of bluegill Lepomis macrochirus by oral administration of various doses of estradiol-17β (E₂) and evaluated their effects on the growth performance, production and gonadal structure of sex-reversed female bluegill at both sex ratio and histological levels. With positive control treatment, 30-day-old fry were fed with E₂ at 50, 100, 150 and 200 mg kg⁻¹ diet for 60 days. The survival of fish in the E₂ treated and control groups was not significantly different (P >0.05). The growth of the treated fish was significantly retarded during the period of treatment, while there was no side effect detected post-treatment and the retarded fish caught up during 120 days of culture after E₂ treatment. All the treated groups produced 100% monosex female populations based on the macroscopic shape of gonads, and there were no significant differences detected between any E₂ treatment and control group in the mean GSI of females during the spawning season from June to October (P >0.05). Histologically, 13.3% and 5.0% of the intersex fish were determined to come from the 50 and 100 mg kg⁻¹ E₂ treatment groups, respectively, with 6.9% and 4.1% of the gonadal area containing spermatocytes. Most of genotypical male fish treated with exogenous E₂ developed gonadal structures histologically indistinguishable from the gonads of females. This study suggests that 150 mg kg⁻¹ E₂ is the optimal dosage for feminization in bluegill, with 50 and 100 mg kg⁻¹ E₂ being sub-optimal and 200 mg kg⁻¹ E₂ being over-optimal.
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