Breed W G, Leigh C M
Department of Anatomy and Histology, University of Adelaide, Australia.
Gamete Res. 1988 Feb;19(2):131-49. doi: 10.1002/mrd.1120190204.
The aim of the present study was to determine the morphological changes that take place in the male and female gametes during in vivo fertilization in the Australian marsupial, the fat-tailed dunnart, Sminthopsis crassicaudata. Plastic sections were cut of sperm and eggs recovered from the oviducts of recently mated individuals, and light microscopy of thick, and transmission EM of thin, sections was carried out. It was found that, before penetration of the zona, the spermatozoon came to lie along the outer surface with its rostral tip forming a depression in the zona substance. During penetration, zona material was packed tightly around the spermatozoon, and no large hole was formed. A spermatozoon within the perivitelline space had made contact with the oolemma by way of its apical tip. In a spermatozoon partly incorporated into the ooplasm, fusion appeared to have taken place between its plasma membrane and that of the oolemma. Mucoid coat material became deposited outside the zona at this time; its existence and/or the release of cortical granule content probably prevented polyspermy. Once inside the egg cytoplasm, the sperm head sometimes travelled a considerable distance before chromatin decondensation occurred. In addition, it appeared to rotate somewhat on its axis at this time. Finally, some membranous structures were found around two condensed sperm heads in the ooplasm, which may have been part of the pronuclear envelope. Thus this study on in vivo fertilization in the dunnart documents, for the first time, some aspects of fertilization in an Australian marsupial as seen with the transmission electron microscope; it indicates a few differences from those previously found for the American opossum.
本研究的目的是确定澳大利亚有袋动物肥尾袋鼬（Sminthopsis crassicaudata）体内受精过程中雄性和雌性配子发生的形态变化。对从近期交配个体的输卵管中回收的精子和卵子进行塑料切片，对厚切片进行光学显微镜观察，对薄切片进行透射电子显微镜观察。结果发现，在穿透透明带之前，精子沿着其外表面排列，其头部前端在透明带物质中形成一个凹陷。在穿透过程中，透明带物质紧密包裹在精子周围，没有形成大洞。卵周隙内的精子通过其顶端与卵质膜接触。在部分融入卵质的精子中，其质膜与卵质膜之间似乎发生了融合。此时，黏液样被膜物质沉积在透明带外；其存在和/或皮质颗粒内容物的释放可能防止了多精受精。一旦进入卵细胞质，精子头部有时会在染色质解聚之前移动相当长的距离。此外，此时它似乎会绕轴旋转。最后，在卵质中两个浓缩的精子头部周围发现了一些膜状结构，它们可能是原核膜的一部分。因此，这项关于肥尾袋鼬体内受精的研究首次用透射电子显微镜记录了澳大利亚有袋动物受精的一些方面；它表明与之前在美国负鼠中发现的情况存在一些差异。
