The union between a sperm and an egg nucleus in egg fertilization is necessary to mix genetic materials to create a new diploid genome for the next generation. In most animals, only one sperm is incorporated into the egg (monospermy), but several animals exhibit physiological polyspermy in which several sperms enter the egg during normal fertilization. However, only one sperm nucleus forms the zygote nucleus with the egg nucleus, even in a polyspermic egg. The cellular and molecular mechanisms involved in the selection of sperm nuclei in the egg cytoplasm have been well investigated in urodele amphibians. The principal sperm nucleus develops a larger sperm aster and contacts the egg nucleus to form a zygote nucleus, whereas other accessory sperm nuclei are unable to approach the egg nucleus. The diploid zygote nucleus induces cleavage and participates in embryonic development, whereas the accessory sperm nuclei undergo pyknosis and degenerate. We propose several models to account for the mechanisms of the selection of one sperm nucleus and the degeneration of accessory sperm nuclei. The roles of physiological polyspermy in animal reproduction are discussed by comparison with other polyspermic species.

中文翻译：

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生理多精子：选择精子核以发育两栖动物的二倍体基因组。

卵子受精过程中精子与卵子核之间的结合对于混合遗传物质以创造下一代的新二倍体基因组是必不可少的。在大多数动物中，卵中仅掺入一个精子（单精子），但是一些动物表现出生理上的多精子，在正常的受精过程中，有几个精子进入卵子。但是，即使在多精卵中，也只有一个精子核与卵核一起形成合子核。在卵两栖动物中已经充分研究了卵细胞质中精子核的选择所涉及的细胞和分子机制。主要的精子核发育出较大的精子，并与卵核接触形成合子核，而其他精子副核则无法接近卵核。二倍体合子核诱导卵裂并参与胚胎发育，而精子副核则发生缩并变性。我们提出了几种模型来解释一个精子核的选择和附属精子核的退化的机制。通过与其他多精子种类进行比较，讨论了生理多精子在动物繁殖中的作用。