The Possible Mechanism of Sex Change in the Protandrous Black Porgy, Acanthopagrus schlegeli

黑鯛性轉變之可能機制

杜金蓮(Jin-Lien Du) ； 林碧雲(Bih-Yun Lin) ； 李彥宏(Yan-Hoarn Lee) ； 岳文勛(Wen-Shiun Yueh) ； 黃靜端(Jing-Duan Huang) ； 李孟芳(Mong-Fong Lee) ； 何俊霖(Chun-Lin He) ； 孫藍天(Lian-Tien Sun) ； 張清風(Ching-Fong Chang)

《臺灣水產學會刊》 30卷2期 (2003/06) Pp. 101-119

https://doi.org/10.29822/JFST.200306.0001

摘要

黑鯛是屬於先雄後雌之雌雄同體型海水魚，兩性精巢與兩性卵巢是由結締組織所介隔，因此這種生殖腺的特徵提供為探討魚類性轉變機制之重要模式魚種。黑鯛進入第三年性轉變之雌魚血漿雌二醇與卵黃素前質濃度均比雄魚為高，相反的血漿11-ketotesto sterone濃度則較低。以雌二醇投餵一年及二年齡黑鯛，均會促使黑鯛性轉變，生殖腺的環化酵素及血漿促性腺生成激素濃度亦顯著增高，進一步以環化酵素抑制劑可以完全抑制三年齡黑鯛自然性轉變之發生。經由基因選殖黑鯛estrogen receptor （ERα與ERβ）與androgen receptor (AR)，且測定黑鯛性轉變過程之精巢與卵巢ERα、ERβ與AR基因濃度(mRNA transcripts)，得知兩性精巢ERα與AR基因濃度顯著比兩性卵巢為高，且ERα隨著兩性卵巢轉變為雌性卵巢之過程而增加。因此雌二醇、環化酵素及性類固醇激素受體與黑鯛性轉變之機制有密切之關係。

關鍵字

睪固酮受體 ； 環化酵素 ； 雌二醇 ； 雌性激素受體 ； 生殖腺發育 ； 性轉變 ； 黑鯛。

並列摘要

Black porgy, Acanthopagrus schlegeli Bleeker, a marine protandrous hermaphrodite, is functional male for the first 2 years of life but begin to sexually change to female after the third year. Testicular tissue and ovarian tissue was separated by connective tissue in the bisexual gonad. This sex pattern provides a unique model to study the endocrine mechanism of sex change in fish. The annual profiles of plasma estradiol, vitellogenin and 11-ketotestosterone concentrations in males were significantly different from those in the 3-year-old females. Significantly high levels of plasma estradiol during the prespawning spawning season and low levels of plasma 11-ketotestosterone during the spawning season were observed in the inversing females. No difference of plasma testosterone levels was observed in males and females. Oral administration of estradiol stimulated high levels of gonadal aromatase activity, plasma luteinizing hormone levels and sex change in the 2-year-old fish. Oral administration with aromatase inhibitors for a year further blocked the natural sex change in 3-year-old black porgy and all fish became functional male with spermiation. Transcripts of estrogen receptor and androgen receptor in the ovarian tissue of bisexual gonad are significantly less expressed than those in the bisexual testicular tissue on the basis of a real time-PCR. Estrogen receptor transcripts are much higher in the vitellogenic ovary than those in the bisexual ovarian tissue. It is concluded that estradiol, aromatase and steroid receptors in the gonadal tissue play an important role in the natural and controlled sex change in black porgy.

並列關鍵字

Androgen receptor ； Aromatase ； Black porgy ； Estradiol-17β ； Estrogen receptor ； Gonadal development ； Sex change