宽壳全海笋受精和早期胚胎发育过程的细胞学观察

用普通光镜和石蜡切片技术,系统观察了宽壳全海笋卵子在受精和早期胚胎发育过程中的外形和核相变化。结果发现,宽壳全海笋成熟未受精卵呈梨形或卵圆形,核相处于第一次成熟分裂前期,有明显的生发泡和核仁;精子为鞭毛型,全长(44.042±1.166)μm,头部呈椭圆形,前端的顶体略呈钝锥状;在水温24℃条件下,精、卵混合后,精子迅速附着于卵子表面,启动卵子发育;受精后6~9 min,生发泡逐渐萎缩、破裂,随后精子进入卵内并轻微膨胀;受精后20,30 min,受精卵先后排出第一、第二极体,完成第一次和第二次成熟分裂;成熟分裂结束后,精、卵核体积迅速膨胀,核膜重新出现,形成弥散状的雌、雄原核,雄原核形成略早于雌原核;受精后40 min左右,雌、雄原核在卵子中央以原核联合的方式结合,随后联合核的染色体共同排列在纺锤体的赤道板上,形成第一次有丝分裂的中期分裂相;随着有丝分裂的进行,染色体被纺锤丝拉向两极,结果在受精后约50 min形成2个大小不等的卵裂球,第一次卵裂结束;第二次卵裂过程与第一次卵裂基本相同,只是卵裂方向与第一次卵裂基本垂直,在受精后65~70 min,第二次卵裂完成,形成1大3小4个卵裂球。另外,实验中发现了少量的多精入卵和多极分离现象。

Cytological observation on fertilization and early embryonic development in Barnea dilatata

The changes of nuclear behavior and external shape during fertilization and early embryonic development in Barnea dilatata were consecutively observed by optical microscope and paraffin section method.The results of cytological observation indicated that unfertilized mature eggs of Barnea dilatata were pea-rshaped or egg-shaped and remained at the prophase of the first maturation division with obvious germinal vesicle and nucleolus,while their sperm belonged to the type of flagellum(44.042±1.166)μm in total length)with the elliptical head.At water temperature of 24,sperms quickly attached to the surface of the egg after mix of sperms and eggs.From 6 min to 9 m in after insemination,germinal vesicle gradually got smaller and brokedown eventually.The fertilized eggs released the first and the second polar bodies at about the 20th min and the 30th min respectively.At completion of the second maturation division,sperm nucleus and the haploid female nucleus expanded immediately and developed into the male and female pronuclei which are loose and incompact.The formation of the male pronucleus preceded that of the female pronucleus.About 35 min,the male and female pronuclei matched into an association nucleus after their chromo somes formed respectively in the center of egg.Subsequently,the chromosomes of association nucleus arranged on the metaphase plate of first cleavage.Until about 50 min,the chromosomes were separated equally into two daughter cells which are different evidently in size.The process of the second cleavage was fundam entally similar to the first cleavage,but the cleavage direction was almost vertical to the first cleavage furrow.65~70 min after insemination,the second cleavage has finished and formed four daughter cells,one big and three small.Additionally,the abnormal phenomena of poly sperm and multi-spindles were also observed in the experiment.