Endocrinological studies on reproduction in hynobiid salamanders

在黑色小海豚中，生精小叶排列在传出小管周围，就像风扇的辐条一样。精原细胞位于传出小管近端的小管中。晚期生殖细胞见于传出小管远侧的小管区。类固醇产生细胞和肌样细胞总是存在于间质组织中。精子和排卵在进入繁殖池塘后不久就会发生。所有生精小叶的精子发生是同步发生的，8月份出现精子。从目前的实验结果来看，可以想象，所谓的水驱动不是由刺激性催乳素在低温性火蜥蜴中触发的。雄性火蜥蜴在进入繁殖池塘后不久，在与水生繁殖有关的体型(雄性第二性征)方面表现出明显的变化。这是身体质量、头部宽度和尾部高度的大幅增加。这些饱满的雄性独占刚由雌性储存的卵囊，并使卵受精。偶尔，第二性征发育较差的雄性也会拥抱卵囊。在这种情况下，周围的其他雄性有机会让卵子受精。在8ﾟC的水中单次注射促性腺激素(600IU HCG)后，在进入繁殖池之前的14至18小时内，怀孕雌性在实验中引起排卵。卵囊的形成在注射后至少50小时在子宫内完成。黑腹隐翅虫和延迟性夜蛾幼虫在低温(如6ﾟC)下生长，但不变态。在这些幼体形态的火蜥蜴中，几乎看不到GTH细胞的分化，也没有性腺成熟。因此，可以想象，通过将低温性火蜥蜴保持在低温下，人工诱导其新生是困难的。

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.