Twan Wen-Hung, Hwang Jiang-Shiou, Lee Yan-Horn, Wu Hua-Fang, Tung Ying-Hsiu, Chang Ching-Fong
National Museum of Marine Biology and Aquarium, Pingtung 944, Taiwan, ROC.
Comp Biochem Physiol A Mol Integr Physiol. 2006 Jul;144(3):247-53. doi: 10.1016/j.cbpa.2006.01.011. Epub 2006 Feb 20.
Most broadcast spawning scleractinian corals synchronously release gametes during a brief annual spawning period. In southern Taiwan, the mass spawning of scleractinians occurs in lunar mid-March. The exact cues triggering this annual phenomenon remain unclear. A scleractinian coral, Euphyllia ancora has been selected as a model for the hormones and reproduction studies. 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, glucuronided E2 and T were obtained in the coral tissue just prior to spawning. The presence of specific aromatase activity was demonstrated in coral tissue. 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) was detected and quantified in coral tissue. 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). Peak levels of irGnRH were detected during the spawning period. In in vivo experiments, mGnRH agonist time- and dose-dependently stimulated aromatase activity, as well as the levels of T and E2 in free and glucuronided forms in coral. In conclusion, our data suggest that irGnRH and glucuronided E2 may play important roles in the control of reproduction and mass spawning in corals.
大多数进行散播式产卵的石珊瑚在每年短暂的产卵期内同步释放配子。在台湾南部，石珊瑚的大规模产卵发生在农历三月中旬。引发这一年度现象的确切线索仍不清楚。一种石珊瑚，脑纹珊瑚已被选为激素与繁殖研究的模型。全年在珊瑚虫体内均能识别并持续检测到游离形式和葡萄糖醛酸化形式的睾酮（T）和雌二醇（E2）。在产卵前，珊瑚组织中游离E2、葡萄糖醛酸化E2和T的水平达到峰值。在珊瑚组织中证实存在特定的芳香化酶活性。全年在珊瑚组织中检测到的游离E2浓度高于葡萄糖醛酸化E2。相比之下，在珊瑚大规模产卵期间，海水中葡萄糖醛酸化E2的水平高于游离E2和葡萄糖醛酸化T。此外，在珊瑚组织中检测并定量了免疫反应性促性腺激素释放激素（irGnRH）的免疫反应性和生物活性。珊瑚提取物（irGnRH）和哺乳动物（m）GnRH激动剂对黑鲷垂体细胞（体外）中促黄体生成素（LH）的释放具有相似的剂量依赖性作用。在产卵期检测到irGnRH的峰值水平。在体内实验中，mGnRH激动剂对珊瑚中芳香化酶活性以及游离和葡萄糖醛酸化形式的T和E2水平具有时间和剂量依赖性刺激作用。总之，我们的数据表明，irGnRH和葡萄糖醛酸化E2可能在珊瑚繁殖和大规模产卵的控制中发挥重要作用。
