The effects of exogenous androgens on ovarian development and sex change in female orange-spotted protogynous grouper, Epinephelus coioides

摘要

The efficacy of various doses of an androgen mixture, containing testosterone (T), 17alpha-methyltestosterone (MT), and testosterone propionate (TP) in equal ratios, for induction of sex change in protogynous orange-spotted grouper, Epinephelus coioides, was examined. The androgen mixture, with doses from 1 to 20,000 mug/kg BW, was implanted into each fish (body weight 1.7 kg) in July (post-spawning season), and gonadal stage and plasma T were monitored at various time intervals for a period of 90 days. Gonadosomatic (GSI) and hepatosomatic indices (HSI), gonadal histology, sex steroids T, 11-ketotestosterone= 11-KT, and estradiol=E2) in plasma were determined after 90 days of implantation. The implanted T was released to plasma for 60 days. All androgen mixtures at doses higher than 1000 mug/kg BW were capable of inducing a sex transition and completion of spermatogenesis up to the functional male phase. Low doses of androgens induced ovarian development and higher GSI and HSI indices than in the control and other groups. Significantly higher plasma T levels were found in the developing and spermiating males as compared to the females and intersex-transitional fish. No significantly difference of plasma levels of E2 and 11-KT was found in the control and all the androgen-treated groups (during the nonreproductive season). Therefore, it is concluded that the stimulation of sex change or ovarian development is dependent on the dose and time course of implanted androgens. Plasma T levels were correlated with the development of controlled male phase in protogynous grouper, E. coioides.