Takahashi Shigekazu, Nakazawa Hiromi, Watanabe Akihiko, Onitake Kazuo
Department of Biology, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan.
J Exp Zool A Comp Exp Biol. 2006 Dec 1;305(12):1010-7. doi: 10.1002/jez.a.295.
The significance of egg-jelly layers in internal fertilization was evaluated in the newt, Cynops pyrrhogaster. In this species, six egg-jelly layers, J1, J2, J3, J4, J5 and the outermost J6 layers, are accumulated on the surface of the fertilizable eggs in pars convoluta of the oviduct. When a large number of sperm (about 6 x 10(5)) were placed on eggs having different numbers of jelly layers, all the eggs were fully fertilized, although many of the eggs developed abnormally. Upon insemination using about 600 sperm, only eggs with the full set of jelly layers were fertilized at a high rate with normal development. Since around 300 (the range of 48-1,192) sperm were observed on and in the egg-jelly in naturally spawned eggs, we conclude that the J6 layer must be present on the outermost surface of the egg-jelly for successful internal fertilization of the newt. Previous studies have suggested that the J6 layer is a prerequisite for the initiation of sperm motility and the acrosome reaction. In the present study, the fertilization rate decreased in eggs with a full set of jelly layers when inseminated using acrosome-reacted and motile sperm. However, the fertilization rate was high when motile sperm with intact acrosome was used. These results suggest that induction of the sperm acrosome reaction in the J6 layer is an important step in the internal fertilization of the newt.
在东方蝾螈（Cynops pyrrhogaster）中评估了卵胶层在体内受精中的重要性。在该物种中，六个卵胶层，即J1、J2、J3、J4、J5和最外层的J6层，在输卵管卷曲部可受精卵子的表面积累。当将大量精子（约6×10⁵个）置于具有不同数量卵胶层的卵子上时，所有卵子均能完全受精，尽管许多卵子发育异常。使用约600个精子进行授精时，只有具有完整卵胶层的卵子能以较高的受精率正常发育。由于在自然产出的卵子的卵胶内外观察到约300个（范围为48 - 1192个）精子，我们得出结论，对于东方蝾螈成功进行体内受精，J6层必须存在于卵胶的最外表面。先前的研究表明，J6层是精子运动启动和顶体反应的先决条件。在本研究中，当使用已发生顶体反应且具有运动能力的精子进行授精时，具有完整卵胶层的卵子的受精率降低。然而，当使用顶体完整且具有运动能力的精子时，受精率较高。这些结果表明，在J6层诱导精子顶体反应是东方蝾螈体内受精的重要步骤。
