Conserved Roles of Hormones in the Reproduction of the Scleractinian Coral Euphyllia ancora

本文主要探討內分泌因子與雌性腎形真葉珊瑚每年集體排放卵束的關係。由腎形真葉珊瑚可測得性類固醇激素（睪固酮及雌二醇），另亦發現珊瑚含有醣基化性類固醇激素。珊瑚雌二醇及醣基化雌二醇濃度及芳香化酵素活性隨著珊瑚卵成熟而顯著增加，並在生殖季節達到高峰，顯示性類固醇激素在珊瑚卵細胞成長與成熟的重要性，且證明珊瑚有自行合成雌二醇的能力。珊瑚並含有促性腺激素釋放素(GnRH)，其濃度亦在生殖季節達到最高峰。且珊瑚GnRH會促進黑鯛腦下垂體細胞分泌促性腺生成激素(LH)的分泌，相反的哺乳動物GnRH受體的拮抗物則會抑制珊瑚GnRH對魚類腦下垂體細胞分泌LH的促進作用。哺乳動物GnRH會進一步顯著促進珊瑚芳香化酵素活性、自由態與醣基化的睪固酮與雌二醇的濃度。由本文的研究，推測GnRH與醣基化雌二醇在雌性腎形真葉珊瑚生殖扮演重要的角色。

關鍵字

珊瑚；激素；生殖；排卵；性類固醇激素；促性腺激素釋放素

並列摘要

In southern Taiwan, the mass spawning of scleractinians occurs in lunar mid-March. We hypothesize that the endocrine system plays an important role as an endogenous factor in the synchronous mass spawning of scleractinian corals, using Euphyllia ancora as a model species. Testosterone (T) and estradiol (E2) in free and glucuronided forms were identified and consistently detected in coral polyps throughout the year. Peak levels of free E2 and glucuronided E2 were obtained in the coral tissue just prior to spawning. The presence of specific aromatase activity was demonstrated in coral tissue, with a significantly high aromatase activity detected during the spawning period. Higher concentrations of free E2 than glucuronided E2 were detected in the coral tissue throughout the year. In contrast, higher levels of glucuronided E2 than free E2 and glucuronided T were found in seawater during mass coral spawning. Furthermore, immunoreactivity and biological activity of immunoreactive gonadotropin-releasing hormone (irGnRH) were detected and peak levels of irGnRH were observed in coral tissue during spawning. Coral extracts (irGnRH) and mammalian (m) GnRH agonist had a similar dose-dependent effect on luteinizing hormone (LH) release in black porgy fish pituitary cells (in vitro); while mGnRH receptor antagonist specifically blocked the stimulatory effects of coral irGnRH. In in vivo experiments, mGnRH agonist time-and dose-dependently stimulated aromatase activity as well as levels of T and E2 in free and glucuronided forms in E. ancora. In conclusion, our data suggest that irGnRH and glucuronided E2 may play important roles in the control of reproduction and mass spawning in corals.

並列關鍵字

Coral ； Hormone ； Reproduction ； Sex steroids ； Gonadotropin-releasing hormone

國際替代計量

Conserved Roles of Hormones in the Reproduction of the Scleractinian Coral Euphyllia ancora

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