Mechanisms of multiple spawning of teleosts

关于硬骨鱼性腺成熟机制的许多信息已以单产卵物种（如鲑科鱼）为模型收集。本研究以多次产卵的鲤科鱼——玫瑰苦鱼为模型进行了多次产卵研究。短生殖周期中促性腺细胞精细结构的变化：苦麻的短生殖周期分为三个阶段；排卵期前，排卵期和产卵后。仅在垂体远端近部观察到一种类型的促性腺激素。在整个循环过程中，小颗粒的大小和数量没有明显变化。然而，大球（LG）的大小发生了巨大变化；排卵期LG直径为13000 ~ 15000*，产卵期增大到15000 ~ 28000*，产卵后减小到7500 ~ 12500*。短生殖周期卵巢体外类固醇生成：卵黄积累卵母细胞分为两组；排卵前大卵母细胞（长直径1.2-1.7 mm）和小卵母细胞（长直径0.6-1.1 mm）。LO或SO分别加入或不加入鲑鱼垂体提取物（SPE， 10或100马克/毫升）或妊娠母马血清促性腺激素（PMSG， 10或100 IU/毫升）孵育。在产卵后的鱼类中，根据外用促性腺激素的作用，LO和SO产生的雌二醇17 - β （E2，促卵黄激素）和17,20 -二羟基-4-孕激素-3-酮（17,20f - β - P，促卵母细胞成熟激素）的量几乎相同。然而，在排卵期前的鱼中，SO的E2产量远高于LO。与SO相比，LO在促性腺激素作用下产生了大量的17,20 β - p。

Much information on the mechanisms of gonadal maturation in teleosts has been collected using single spawning species, such as salmonids, as a model. In this study the rose bitterling Rhodeus ocellatus ocellatus, a multiple spawning cyprinid was used as a model for multiple spawners.1. changes in fine structure of gonadotrophs during short reproductive cycle : Short reproductive cycle of the bitterling was divided into three phases ; pre-ovulation, ovulation, and post-spawning. Only one type of gonadotroph was observed in the proximal pars distalis of the pituitary. Throughout the cycle, the size and number of small granules did not change significantly.However, the size of large globules (LG) changed drastically ; the diameter of LG was 13000-15000* in the pre-ovulation phase, then it increased to 15000-28000* in the spawning phase, and decreased to7500-12500* in the post-spawning pahse.2. In vitro steroid production in the ovary during short reproducitve cycle : Yolk accumulated oocytes were divided into two groups ; pre-ovulating large oocytes (LO, longer diameter 1.2-1.7 mm) and small oocytes (SO, 0.6-1.1 mm) .LO or SO were incubated with or without salmon pituitary extract (SPE ; 10 or 100 mug/ml) or pregnant mare serum gonadotropin (PMSG ; 10 or 100 IU/ml) . In the post-spawning fish, both LO and SO produced almost the same amount of estradiol 17beta(E2 ; yolk production stimulating steroid) and 17, 20beta-dihydroxy-4-pregnen-3-one (17, 20fbeta- P ; oocyte maturation inducing steoid) in accordance with the administration of external gonadotropin. In the pre-ovulation fish, however, the production of E2 was much higher in SO than that in LO.In contrast, LO produced large amount of 17, 2Obeta-P compared to that produced by SO in response to gonadotropin administration.