黄颡鱼受精早期精子入卵扫描电镜观察

Scanning Electron Microscopic Observation on the Sperm Penetration into Eggs in Pseudobagrus fulvidraco

用扫描电镜对黄颡鱼(Pseudobagrus fulvidraco)成熟精、卵及授精早期精子入卵过程进行了观察。成熟精子为鞭毛型形态,全长为11·2～12·4μm,头部直径1·1～1·3μm,鞭毛长10·0～11·3μm。成熟的黄颡鱼卵呈圆形,具单一受精孔,卵膜上以受精孔为中心分布有无数辐射状沟嵴。授精前,受精孔暴露在外面;授精2s时,受精孔被纤维状物质覆盖,之后大量精子很快黏附在覆盖物上;至授精10s,漏斗状受精孔又暴露出来。黄颡鱼在授精10s～1min内完成精子入卵过程,可观察到几乎所有样品的精孔区出现一圈环状隆起。大量精子处于隆起外侧,只有少数越过隆起到达受精孔前庭。授精1·5min,精孔区的隆起变成两圈,精子鞭毛解体。授精3min,可见迟到的精子被挡在外面。授精5min,精孔区的精子头部解体,受精孔几乎被分泌物覆盖,受精塞清晰可见。至授精20min,精子几乎全部解体。讨论了精子入卵的动力作用、精卵识别和单精受精机制。

The mature eggs, spermatozoa and fertilization process were observed by scanning electron microscopy in Pseudobagrus fulvidraco. The spermatozoa consist of two parts, the head and the tail. The total length of the spermatozoa is 11.2 to 12.4 μm. The diameter of sperm head is 1.1 to 1.3 μm and the length of the tail is 10.0 to 11.3 μm. The mature eggs of P. fulvidraco are elliptical and have a single micropyle on the animal pole, from which there are many fossae and ridges radiating from the egg surface. The micropyle is exposed before insemination and covered with fibroid slipcover at 2 s after insemination. Soon after that, numerous spermatozoa adhere on it. The fibroid slipcover disappeares and the micropyle is exposed at 10 s. The process of sperm penetration into eggs is carried out between 10 s and 1 min and a circle of annular apophysis encircles the micropyle on the egg membrane. Only few spermatozoa can go through the apophysis and reach the vestibule of micropyle. The tail of spermatozoa around the micropylar is disorganized at 1.5 min after insemination and the head is disrupted at 5 min. During this period, the annular apophysis disappears soon after two circles form and fertilization plugs appear, resulting in the block of sperm penetration. Almost all of the spermatozoa on the microovlar region are dissolved in 20 min. In this paper, the chemical recognition of spermatozoa and eggs and the mechanism of monospermy are also discussed.