Growth, sexual transition, and maturation of blacktip grouper Epinephelus fasciatus under long-term artificial rearing: Puberty and its associated physiological and endocrine changes
Growth, sexual transition, and maturation of blacktip grouper Epinephelus fasciatus under long-term artificial rearing: Puberty and its associated physiological and endocrine changes
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DOI：
10.1016/j.aquaculture.2022.738595
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发表时间：
2022-07
期刊：
影响因子：
4.5
通讯作者：
Nhan Thành Phạm;T. Amagai;Yuji Mushirobira;R. Murata;K. Soyano
中科院分区：
文献类型：
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作者：
Nhan Thành Phạm;T. Amagai;Yuji Mushirobira;R. Murata;K. Soyano
黑鳍石斑鱼是一种珍贵的海水养殖鱼类。本研究的目的是获得信息的青春期的年龄，生长性能，性腺发育，性转变模式，和血浆性类固醇水平从少年阶段到成熟的标本在圈养饲养。性腺发育的阶段进行了鉴定组织学分析，血浆性类固醇水平进行了测定，使用酶联免疫吸附测定。我们的研究结果表明，成熟和产卵的黑鳍石斑鱼发生在近3岁，虽然一些女性成熟2年。血浆17β-雌二醇（E2）水平在3岁时的青春期迅速升高，尤其是在卵黄形成后期的第三卵黄期，在产卵前的成熟期和排卵期下降。性腺体细胞指数也表现出增加与血浆E2水平的上升一致。血浆11-酮睾酮（11-KT）水平显着增加，在性别变化和男性。血浆E2水平的显著下降和11-KT水平的显著升高是导致这些鱼性别转变的关键因素。有趣的是，在1岁3个月的年龄未成熟的女性卵巢中的精母细胞的伴随出现。黑鱼石斑鱼的性别转换和雄性鱼的最早出现在2年，虽然没有成熟的女性观察到低于这个年龄。这表明，这些鱼的性别变化和雄性转换发生在没有经过成熟的雌性阶段。总之，该物种有能力在2岁时达到青春期，但大多数个体在3岁时成熟并具有功能。青春期可能受年龄而不是大小的影响。此外，虽然这个物种有一个雌雄同体的模式，但当同一年出生的个体被一起抚养时，有些个体能够直接成为雄性而不经历成熟的雌性阶段。这是由于在圈养环境中缺乏社会化，不同年龄的个体不能共存，这与野生环境不同。
The blacktip grouperEpinephelusfasciatusis considered a valuable marine fish for aquaculture. This study was conducted to obtain information on its age of puberty, growth performance, gonadal development, sexual transition pattern, and plasma sex steroid levels from juvenile stage to maturity in specimens reared in captivity. The stages of gonadal development were identified by histological analysis, and plasma sex steroid levels were measured using an enzyme-linked immunosorbent assay. Our results show that maturation and spawning in blacktip groupers occurred at almost 3 years of age; although some females matured at 2 years. Plasma 17β-estradiol (E2) levels increased rapidly to high levels during puberty at 3 years of age, especially during the late stage of vitellogenesis at the tertiary yolk stage, and reduced at the ripe and ovulated stages prior to spawning. The gonadal somatic index also showed an increase consistent with the rise in plasma E2levels. Plasma 11-ketotestosterone (11-KT) levels increased dramatically during sex change and in males. The significant decrease in plasma E2levels and remarkable increase in plasma 11-KT were the key factors for the progress of sex change in these fish. Interestingly, there were the concomitant appearances of spermatocytes in ovaries of immature females at 1 year 3 months of age. The earliest appearance of sex-transitioning and male fish in blackfish groupers was observed at 2 years, although no mature females were observed below this age. This indicated that the sex change and male transformation in these fish took place without them undergoing the mature female stage. In conclusion, this species had the ability to reach puberty at 2 years of age, but most individuals matured and were functional at 3 years old. Puberty might be affected by age rather than size. In addition, although this species had a protogynous hermaphrodite pattern, when individuals born in the same year were reared together, some individuals were capable of directly becoming males without experiencing a mature female stage. This was due to the lack of socialization in captivity wherein individuals of various ages do not coexist, unlike that in the wild.