Endocrine evidence that silvering, a secondary metamorphosis in the eel, is a pubertal rather than a metamorphic event
Endocrine evidence that silvering, a secondary metamorphosis in the eel, is a pubertal rather than a metamorphic event
复制标题
DOI：
10.1159/000092642
复制
发表时间：
2005-01-01
影响因子：
4.1
通讯作者：
Dufour, Sylvie
中科院分区：
文献类型：
--
作者：
Aroua, Salima;Schmitz, Monika;Dufour, Sylvie
银化(从黄鳗转变为银鳗)传统上被认为是一种变态，因为它在形态、生理和行为上发生了许多变化，为鳗鱼的海洋迁徙做好了准备。然而，一些变化，如性腺重量增加和类固醇生成，表明银化也可以被认为是青春期事件。为了评估哪个内分泌轴可能参与了银化的诱导，我们比较了从黄色到银色雌性鳗鱼转变过程中脑垂体和外周激素的变化。在镀银过程中，促性腺激素轴被强烈激活。卵泡刺激素(FSH)的信使核糖核酸水平在白银早期升高，随后黄体生成素(蛋白质和信使核糖核酸)水平升高。此外，血浆性类固醇(雌二醇、雌二醇；睾酮、睾酮和11-酮-睾酮)和卵黄原蛋白水平显著升高。相反，促甲状腺激素mRNA水平没有变化，血浆甲状腺激素没有或微弱变化，这表明在镀银过程中促甲状腺轴没有或适度变化。同样，促生长激素轴没有被激活，如垂体生长激素表达(蛋白质和mRNA)和血浆水平所表明的那样。此外，我们还研究了长期使用甲状腺激素(T4)和性激素(T和E_2)处理雌性黄鳗对其生物计量特性的影响。T可引起眼球增大，消化道缩小，而T_4和E_2对此无影响。这些荷尔蒙特征和实验数据得出的结论是，鳗鱼的银化应该被认为是青春期的开始，而不是“真正的”变态。版权所有(C)2005年S.Karger AG，巴塞尔。
Silvering (transition from yellow to silver eel) has been traditionally considered as a metamorphosis in view of the numerous morphological, physiological and behavioral changes preparing the eel for the oceanic migration. However, some changes, such as increases in gonad weight and steroidogenesis, suggest that silvering could also be considered as a pubertal event. In order to assess which endocrine axis may be involved in the induction of silvering, we compared the profiles of pituitary and peripheral hormones during the transition from yellow to silver female eels. A strong activation of the gonadotropic axis was shown during silvering. Follicle-stimulating hormone (FSH) mRNA levels increased during the early stages of silvering, followed by a later increase in luteinizing hormone (protein and mRNA) levels. In addition, plasma levels of sexual steroids (estradiol, E2; testosterone, T, and 11-ketotestosterone) and of vitellogenin significantly increased. In contrast, thyrotropin mRNA levels did not change and no or weak variations in plasma thyroid hormones were observed, indicating no or moderate change of the thyrotropic axis during silvering. Similarly, the somatotropic axis was not activated, as shown by pituitary growth hormone expression (protein and mRNA) and plasma levels. In addition, we studied the effects of chronic treatments of female yellow eels with thyroid hormone (thyroxine, T4) and sex steroids (T and E2) on biometrical parameters characteristics of silvering. T induced an increase in eye size and a reduction of digestive tract, whereas T4 and E2 had no effect. These hormonal profiles and experimental data lead to the conclusion that eel silvering should be considered as an onset of puberty rather than a 'genuine' metamorphosis. Copyright (c) 2005 S. Karger AG, Basel.