生物時計と潮汐によるサンゴ礁棲ベラ類の産卵時刻あわせ

珊瑚礁中的许多濑鱼每天都在白天涨潮时产卵。在这项研究中，我们研究了潮汐相关的卵巢发育的三斑濑鱼Halichoeres trimaculatus，这是一种常见的物种在珊瑚礁的印度太平洋。当鱼被收集在不同的潮汐阶段，在早上，性腺指数（GSI）和卵巢组织学的变化，伴随着GSI的增加，走向高潮，离合器的最先进的卵母细胞从卵黄发生成熟阶段。涨潮前后大部分卵巢中存在排卵卵和排卵后卵泡（POF），落潮前后只有POF残留，表明产卵发生在涨潮期间或之后。我们注意到，潮汐相关的产卵是显着的，在上午和下午高潮收集的卵巢表现出后产卵功能。有人建议，某些labrid物种具有可塑性，就其产卵时间和利用其繁殖成功的有力的环境线索。当卵巢碎片与前体类固醇一起孵育时，在高潮和落潮期间，睾酮向17β-雌二醇的转化率较高，而在低潮和涨潮期间，观察到17α-羟孕酮向17α，20 β-二羟基-4-生育烯-3-酮和17α，20 β，21-三羟基-4-生育烯-3-酮的转化。用人绒毛膜促性腺激素孵育卵巢碎片导致类固醇激素随潮汐的类似波动。这些类固醇激素的产生与卵巢中卵母细胞的发育有关，可能受促性腺激素的调节。这些结果表明，日周期是卵母细胞发育的基础，潮汐周期叠加在这个过程中。

Many wrasses in coral reefs exhibit daily spawning that peaks around daytime high tide. In this study, we examined tidal-related ovarian development in the threespot wrasse Halichoeres trimaculatus, which is a common species in coral reefs of the Indo-Pacific Ocean. When the fish were collected in the morning at different tidal phases, the gonadosomatic index (GSI) and ovarian histology changed; concomitant with increases in GSI towards high tide, a clutch of the most advanced oocytes developed from vitellogenic to maturation stages. Ovulated eggs and post-ovulated follicles (POF) existed in most ovaries around high tide, but only POF remained around ebb tide, suggesting that spawning occurred during or after high tide. We noticed that tidal-related spawning was remarkable in the morning and that most ovaries collected at afternoon high tide exhibited post-spawning features. It was suggested that certain labrid species possess plasticity with regard to their spawning time and utilize potent environmental cues for their reproductive success. When the ovarian pieces were incubated with precursor steroids, high conversion of testosterone to 17β-estradiol occurred during high and ebb tides, while that of 17α-hydroxyprogesterone to 17α,20β-dihydroxy-4-pregnen-3-one and 17α,20β,21-trihydroxy-4-pregnen-3-one was observed during low and flood tides. Incubation of the ovarian pieces with human chorionic gonadotropin resulted in similar fluctuations of the steroid hormones with tide. Production of these steroid hormones correlated with oocyte development in the ovaries and was probably regulated by gonadotropin. These results demonstrate that the daily cycle is fundamental for oocyte development, and the tidal cycle is superimposed on this process.