Living organisms have adapted to environmental oscillations in light and temperature through evolving biological clocks. Biological rhythms are pervasive at all levels of the endocrine system, including the somatotropic (growth) axis. The objective of the present research was to study the existence of daily rhythms on the somatotropic axis of a marine teleost species, specifically, the gilthead sea bream (Sparus aurata). Larvae of S. aurata at 30 dph (days post hatching), kept under a 9 L:15D (light-dark) photoperiod, were collected every 3 h throughout a 36 h cycle. The expression of the following somatotropic axis genes was analyzed by quantitative PCR: pituitary adenylate cyclase-activating polypeptide 1 (adcyap1), prepro-somatostatin-1 (pss1), growth hormone (gh), growth hormone receptor types 1 and 2 (ghr1 and ghr2, respectively), insulin-like growth factor 1 (igf1) and igf1 receptor a (igf1ra). All genes displayed significant differences among time points and, with the exception of adcyap1, all showed statistically significant daily rhythms. The acrophases of gh, ghr1, ghr2, igf1 and igf1ra were located around the end of the dark phase, between ZT19:44 and ZT0:48 h, whereas the highest expression levels of adcyap1 occurred at ZT18 h. On the other hand, the acrophase of pss1, an inhibitor of Gh secretion, was located at ZT10:16 h, hence it was shifted by several hours with respect to the other genes. The present results provide the first thorough description of somatotropic axis rhythms in gilthead sea bream. Such knowledge provides insights into the role of rhythmic regulation of the Gh/Igf1 axis system in larval growth and metabolism, and it can also improve the implementation of more species-specific feeding regimes.

生命有机体通过不断发展的生物钟适应了光和温度的环境振荡。生物节律普遍存在于内分泌系统的各个层面，包括生长（生长）轴。本研究的目的是研究海洋硬骨鱼类，特别是金头鲷（Sparus aurata）的生长轴上的日常节律的存在。幼虫S.头鲷在30 DPH（天后孵化），一个9升下保持：15D（明暗）光周期，收集在整个36小时周期，每3小时。通过定量PCR分析以下促生长轴基因的表达：垂体腺苷酸环化酶激活多肽1（adcyap1），前促生长抑素-1（pss1），生长激素（gh），生长激素受体1型和2型（分别为ghr1和ghr2），胰岛素样生长因子1（igf1）和igf1受体a（igf1ra）。所有基因在时间点之间均显示出显着差异，除adcyap1外，所有基因均具有统计学上的显着每日节律。的峰值位相GH，GHR1，GHR2，IGF1和igf1ra它们位于黑暗阶段的末尾，在ZT19：44和ZT0：48 h之间，而adcyap1的最高表达水平发生在ZT18 h。另一方面，抑制Gh分泌的pss1的顶相位于ZT10：16 h，因此相对于其他基因而言，它偏移了几个小时。目前的结果提供了首次全面描述银头鲷的生长激素轴节律。这些知识为Gh / Igf1轴系统的节律性调节在幼虫生长和代谢中的作用提供了见识，并且还可以改善对特定物种的喂养方案的实施。