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Endocrinological studies on reproduction in hynobiid salamanders

小鲵繁殖的内分泌学研究

基本信息

批准号：
01540615
负责人：
IWASAWA Hisaaki
金额：
$ 1.34万
依托单位：
Niigata University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1991
项目状态：
已结题

项目摘要

In Hynobius nigrescens, the seminiferous lobules are arranged around the efferent ductules like the spokes of a fan. The spermatogonia are located in the tubules proximal to the efferent ductules. Germ cells in advanced stages are seen in the tubular regions distal to the efferent ductules. Steroid producing cells and myoid cells are always present within the interstitial tissue. Spermiation and ovulation occur soon after entering the breeding pond. Spermatogenesis occurs synchronously in all seminiferous lobules, and spermatozoa appear in August. From the results of the present experiments, it is conceivable that the so-called water drive is not triggered by the stimulation of prolactin in hynobiid salamanders. Male salamanders show pronounced changes in body shape (male secondary sexual character) associated with aquatic reproduction soon after entering the breeding pond. This is a large increase in body mass, head width and tail height. These well-swelled males monopolize egg sacs just deposited by females, and fertilize the eggs. Occasionally, males with the less developed secondary sexual characters embrace the egg sacs also. In that case, other surrounding males have a chance to fertilize the eggs. Ovulation is experimentally caused in gravid females just before entering the breeding pond between 14 and 18 h after a single injection of gonadotropin (600 IU hCG) in water at 8ﾟC. The formation of egg sacs is completed in the uterus at least 50 h after the injection. The larvae of H. nigrescens and H. retardatus grow at low temperature, such as 6ﾟC, but do not metamorphose under such a condition. In those larval-form salamanders, the differentiation of GTH cells is hardly seen, and gonadal maturation does not occur. It is therefore conceivable that artificial induction of neoteny in hynobiid salamanders by keeping them at low temperatures is difficult.

在 Hynobius nigrescens 中，曲细精小叶像扇子的辐条一样排列在传出小管周围。精原细胞位于传出小管附近的小管中。晚期生殖细胞可见于传出小管远端的管状区域。类固醇产生细胞和肌样细胞始终存在于间质组织内。进入繁殖池后很快发生精子和排卵。所有生精小叶同步发生精子发生，8月出现精子。从目前的实验结果来看，可以想象，小鲵中所谓的水驱动并不是由催乳素的刺激引发的。雄性蝾螈在进入繁殖池后不久就会表现出与水生繁殖相关的体形（雄性第二性征）的显着变化。这是体重、头部宽度和尾部高度的大幅增加。这些肿胀的雄性独占雌性刚产下的卵囊，并使卵子受精。有时，第二性征发育欠佳的雄性也会拥抱卵囊。在这种情况下，周围的其他雄性就有机会使卵受精。在进入繁殖池之前，在 8°C 的水中单次注射促性腺激素 (600 IU hCG) 后 14 至 18 小时，通过实验引起妊娠雌性的排卵。注射后至少50小时，卵囊在子宫内完成形成。 H.nigrescens和H.retatus的幼虫在低温下生长，如6℃，但在这种条件下不会变态。在那些幼虫形式的蝾螈中，几乎看不到GTH细胞的分化，并且性腺不成熟。因此可以想象，通过将小鲵保持在低温下来人工诱导它们的幼态持续是很困难的。