金鱼精子入卵过程的扫描电镜观察

SCANNING ELECTRON MICROSCOPIC OBSERVATIONS ON THE SPERM ENTRY INTO THE EGGS OF GOLDFISH, Carassius auratus

本文采用扫描电镜观察了金鱼(Carassius auratus)卵壳膜(chorion)表面结构和精子入卵过程。在壳膜的卵膜孔(micropyle)区有5—10条沟和嵴。位于精孔管下面,卵的质膜为一束较长的微绒毛组成的精子穿入部(sperm entry site)。授精5s,精子头的顶部已附着于精子穿入部,随即两者的质膜发生融合,而围于精子头部四周的微绒毛迅速伸长形成一受精锥,它不断将精子头部包裹。授精110s,精子的头部和颈部已完全进入卵内,受精锥本身也渐趋消失,但精子尾部仍平躺于卵的表面。皮层小泡是在授精30s后才开始破裂并释放其内含物,导致卵子表面呈蜂窝状,并在无膜内表面附着了大量球状物。

The surface structure of chorion, sperm penetration and exocytosis of cortical alveoli in goldfish, Carassius auratus, were examined by scanning electron microscopy. Five to ten grooves and ridges could be seen in the micropylar region, and they may help the sperms reach the micropyle canal. There was a distinct cluster of microvilli on the plasma membrane, identified as the sperm entry site, beneath the micropyle. The fertilizing sperm attached to the sperm entry site within 5 seconds of the mixing of a gamete suspension. Then, the microvilli of the sperm entry site elongated, fused with plasma membrane of the sperm head and formed a fertilization cone to engulf the sperm head and midpiece. At 110 seconds postinsemination, the sperm head and midpiece were fully incorporated into the egg cytoplasm and the fertilization cone tended to disappear. Exocytosis of cortical alveoli occurred beyond 30 seconds postinsemination. At 90 seconds postinsemination, the whole egg became honeycomb-like structure because of the exocytosis of cortical alveoli and a great number of spherical bodies accumulated on the linner surface of the egg chorion.