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Age-Structured Catch-At-Length Analysis of Bigeye Tuna in the Western and Central Pacific Ocean
年齡結構體長別漁獲量分析法評估中西太平洋大目鮪資源
摘要
經埋植甲基睪固酮60天後，均會對生殖腺切除單邊或不切除之點帶石斑誘導性轉變（由雌性變為雄性），但生殖腺經單邊切除的石斑魚誘導性轉變的速度比不切除生殖腺組為慢。生殖腺切除單邊組經60天埋植後，其單邊生殖腺的重量遠比未切除組顯著的大，顯示生殖腺發育具有補償性的作用，埋植甲基睪固酮亦降低肝臟重量。誘導性轉變成功的雄性石斑魚血漿濃度含有顯著較高的血漿睪固酮，而且血漿睪固酮與雌二醇的濃度比值亦顯著的比雌魚及中間正轉變型為高。
並列摘要
The objectives were to investigate the effects of sex change in the unilateralovariectomized(remained one-side gonad)orange-spotted grouper,Epinephelus coioidesby implantation with 17α-methyltestosterone(MT,10 mg/kg body weight).Two-year-oldfemale groupers(n=42)were equally divided into 6 groups:intact+control implant,intact+MT implant,unilateral ovariectomized+control implant,unilateral ovariectomized+MTimplant,all-ovariectomized+control implant,and all-ovariectomized+MT implant.Oneside of gonad and both sides of gonad were surgically removed in the unilateral and all-ovariectomized groupers,respectively.After 60-day implantation,all the MT-implantedfish(100% in either intact gonad or unilateral ovariectomized groups)changed fromfemales to males.During the process of MT-implantation,intact fish changed to malesafter 15 days(33%),30 days(67%)as compared to 0% on day 15 and 14% on day 30 inthe unilateral ovariectomized fish.Significantly higher gonadosomatic index was detected(P＜0.05)in the unilateral ovariectomized+control implant as compared to other groups.MT implant decreased hepatosomatic index as compared to the respective controlimplanted group.Plasma testosterone(T)concentrations and the ratio of plasmaT/estradiol-17β were correlated to the sex change.No regeneration of gonadal tissue wasobserved in the ovariectomized fish.It is concluded that MT induced sex change ingroupers,E coicoides with either intact or remained single-side gonad.