Liu M, Wang Y-Y, Shan X-J, Kang B, Ding S-X
State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, Fujian, China.
Shandong Provincial Key Laboratory of Fishery Researches and Ecological Environment, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Science, Qingdao, 266071, Shandong, China.
J Fish Biol. 2016 Apr;88(4):1598-613. doi: 10.1111/jfb.12936. Epub 2016 Mar 3.
Gonad ontogeny of the Hong Kong grouper Epinephelus akaara (a bi-directional sex changer) and the yellow grouper Epinephelus awoara (a protogynous hermaphrodite) was examined for the first time from post-larval phase until first sexual maturation, by histology. Approximately 20 specimens of each species were collected randomly every 2-7 weeks from rearing tanks with natural sea water and temperature between June 2013 and June 2014. The paired gonadal primordia (GP) were observed at 6 weeks after hatching (wah) for both species; however, gonia were first observed in GP at 16 wah for E. akaara and at 8 wah for E. awoara. The timings for the appearance of primary-growth stage oocytes (O1) and the completion of ovarian lumen (OL) varied; both at 27 wah for E. akaara, and at 18 and 23 wah for E. awoara respectively. A bisexual-phase gonad with an OL, O1 and scattered spermatogenic cysts (SC) was observed at 27-29 wah for both E. akaara and E. awoara. Sexual differentiation was subsequently observed from the bisexual-phase gonad at 34 wah for E. akaara, and 41 wah for E. awoara, with the appearance of cortical-alveolus stage oocytes (O2) for developing female and the proliferation of SC for developing primary male (i.e. from juvenile directly). Ovaries of mature females contained the vitellogenic stage oocytes (O3) and scattered SC; testes of mature primary males had sperm in sperm sinuses within the gonadal wall and remained O1. Minimum age of first sexual maturation for both female and primary male of E. akaara was at 41 wah; minimum total length (LT ) of female (143 mm) was larger than that of primary male (137 mm L(T)). Minimum age and size of first sexual maturation for female of E. awoara (47 wah and 149 mm L(T), respectively) were larger than those of E. akaara. Developing primary males of E. awoara were found at 41-58 wah, however, mature males were not observed, indicating inconsistency in first sexual maturation for E. awoara. This study provided strong evidences of primary male pathway in E. akaara and E. awoara; the latter is confirmed to be diandric.
首次通过组织学方法，对香港石斑鱼（双向性转变者）和斜带石斑鱼（雌性先熟雌雄同体）从幼体后期直至首次性成熟阶段的性腺发育进行了研究。2013年6月至2014年6月期间，每隔2 - 7周从装有天然海水且水温适宜的养殖池中随机采集每种石斑鱼约20尾样本。两种石斑鱼在孵化后6周（wah）均观察到成对的性腺原基（GP）；然而，香港石斑鱼在16wah时首次在GP中观察到生殖细胞，斜带石斑鱼则在8wah时观察到。初级生长阶段卵母细胞（O1）出现的时间以及卵巢腔（OL）形成的时间有所不同；香港石斑鱼均在27wah时出现，斜带石斑鱼分别在18wah和23wah时出现。在27 - 29wah时，两种石斑鱼均观察到具有OL、O1和散在生精囊肿（SC）的双性期性腺。随后在34wah时，香港石斑鱼从双性期性腺开始出现性别分化，斜带石斑鱼则在41wah时出现，此时发育中的雌性出现皮质泡期卵母细胞（O2），发育中的初级雄性（即直接从幼鱼开始）SC增殖。香港石斑鱼成熟雌性的卵巢含有卵黄生成期卵母细胞（O3）和散在的SC；成熟初级雄性的睾丸在性腺壁内的精子窦中有精子，且仍有O1。香港石斑鱼雌性和初级雄性首次性成熟的最小年龄均为41wah；雌性的最小全长（LT）（143毫米）大于初级雄性（137毫米LT）。斜带石斑鱼雌性首次性成熟的最小年龄和大小（分别为47wah和149毫米LT）均大于香港石斑鱼。在41 - 58wah时发现斜带石斑鱼有发育中的初级雄性，但未观察到成熟雄性，这表明斜带石斑鱼首次性成熟存在不一致性。本研究为香港石斑鱼和斜带石斑鱼的初级雄性发育途径提供了有力证据；后者被证实为双雄性。
