中国对虾受精过程中精卵核的细胞学变化

CYTOLOGICAL CHANGES OF SPERM AND EGG NUCLEI DURING FERTILIZATION IN PENAEUS CHINENSIS

中国对虾精子以其棘部顶端随机附着在卵上 ,精子在凝胶膜形成后 ,第一极体排出前入卵。精子入卵后 ,絮状的精核经过重建形成雄原核。中国对虾卵子排放时处于第一次成熟分裂的中期 ,卵子入海水时 ,纺锤体的长轴与质膜平行。卵子激活后 ,纺锤体的长轴开始旋转 ,旋转至纺锤体长轴与质膜垂直时 ,由纺锤丝牵引着染色体向两极移动 ,外侧的染色体由质膜包裹形成第一极体。受精膜举起后 ,由次级卵母细胞排放出第二极体。此后 ,单倍雌核重建形成雌原核。雄原核形成早于雌原核 ,雌雄原核于卵子中央联会形成联合核。受精后约5 0分钟纺锤丝牵引着染色体移向两极 ,质膜内缢断裂形成两个细胞的胚胎。

When a female prawn spawns, stored spermatozoa were released from the thelycum and mixed with the eggs by the beating of the pleopods. The spermatozoa binded the egg with their spike top by random. At the time when the jelly coat was formed, and before the first polar body was emitted, the sperm penetrated into the egg by crossing the plasma membrane. After the sperm penetrated into the egg, its nucleus was transformed into a big male pronucleus. The eggs of the prawn at spawning were in meiotic metaphase Ⅰ stage, and the meiotic apparatus was positioned parallel to the egg surface. After the egg was activated, the meiotic apparatus rotated and positioned perpendicularly to the egg surface. The chromosomes drawn by the spindle microtubule separated. The chromatin near the plasma membrane was surrounded and formed the first polar body. After fertilization membrane was lifted, the secondary egg emitted the second polar body into the perivitelline space. Following the extrusion of the second polar body, the haploid female chromatin formed a female pronucleus.The male pronucleus formation was earlier than the female's. The male and female pronuclei moved to the center of the egg, and matched into a association nucleus. The chromosomes of the first mitotic apparatus separated 50 min after fertilization and 2 cell embryo was formed by plasma membrane invagination.