单环刺螠受精过程的细胞学观察

Cytological observation of fertilization in Urechis unicinctus

利用组织学和荧光显微镜对单环刺螠（Urechis unicinctus）受精过程中精子入卵以及核相变化进行了观察。结果表明：单环刺螠成熟卵呈卵圆形,核相处于生发泡尚未破裂的第1次成熟分裂前期。在（21±1）℃时,精卵混合后约5 min,精子由卵偏向植物极一侧入卵,受精膜开始举起,继而精核发生第1次膨胀。直至受精后约25 min,受精膜完全举起;受精后10-50 min,卵核相继完成二次成熟分裂,分别形成第一极体和第二极体;受精后50-70 min,精核卵核分别膨胀,形成雄原核和雌原核,进而相向迁移,最后在卵的中央联合形成合子核。受精后70-90 min,受精卵完成第1次卵裂,形成2个大小相等的卵裂球。单环刺螠受精全过程历时约70 min,略长于多数海洋无脊椎动物的受精持续时间。本研究旨在为今后单环刺螠人工育苗和新品种的培育提供基础资料。

We documented the penetration of sperm into the oocyte and the changes in nuclear behavior in Urechis unicinctus using paraffin sections and fluorescent microscopy.The mature oocyte was egg-shaped,had an unbro-ken germinal vesicle,and remained in the prophase of the first maturation division.Sperm rapidly attached to the surface of the oocyte within 5 min of insemination,water temperature（21±1） °C.The sperm penetrated into the oocyte at a location close to vegetal pole triggering development of the fertilization membrane.The sperm nuclei then expanded and the fertilization membrane was completed within 25 min.The first and second maturation divi-sions were completed 10 and 50 min after insemination,and were accompanied by the exclusion of the first and the second polar bodies,respectively.The nuclei of the sperm and egg expanded 50–70 min later,respectively,and developed into the pronuclei.These then migrated to the center of the egg,forming an associated nucleus.The first cleavage was completed after 70–90 min,resulting in two daughter cells.The fertilization process lasted -70 min,which is slightly longer than in most marine invertebrates.Our observations provide basic information for artifi-cial breeding and the cultivation of new varieties of U.unicinctus.