弓獭蛤受精及早期卵裂过程核相变化的细胞学观察

Observation on Cytological Change of Fertilization and Early Cleavage in Lutraria arcuata

采用Hoeehst33258染色和荧光显微镜技术，对弓獭蛤（Lutraria arcuata）受精和早期卵裂过程中的核相变化进行观察．其成熟未受精卵呈圆球形，卵径55～60μm，核相处于第1次成熟分裂前期；精子为鞭毛型，全长约50—55μm．精卵混合后，精予迅速附着于卵子表面；受精后10～30min，精子入卵膨胀成球形；30—50min进行第1次成熟分裂，排出第1极体；50—60min进行第2次成熟分裂，排出第2极俸；同时精核和卵核体积膨胀，形成雄原核和雌原核；70min左右，雌、雄原核联合，形成第1次有丝分裂的中期分裂相；70—90min受精卵进行第1次卵裂，形成2个卵裂球；90～110min进行第2次卵裂，形成1大3小的4个卵裂球．

The fertilized oocytes stained with a fluorescent reagent Hoechst 33258 were observed to study the cytological change of nuclear behavior under a fluorescence microscope. The unfertilized mature oocytes are globular （55 -60 μm in diameter） and remain at the prophase of the first maturation division. The mature sperms （50 - 55 μm in total length） belong to the primitive type. After mixing of sperms and oocytes, sperms quickly attach to the surface of oocytes. After fertilization 10 -30 min, a sperm has penetrated into cytoplasm of a ooeyte and activates the maturation division. The fertilized oocytes release first polar bodies at 30 -50 min and second polar bodies at 50 -60 min. At about 60min, a sperm nucleus and a haploid female nucleus expand to their maximum and develop into a male pronucleus and a female pronucleus which are loose and incompact. At 70 rain, a male pronucleus and a female pronucleus match into an association nucleus after their chromosomes move to the center of the oocyte. At 70 - 90 min, the chromosomes of the zygote are separated equally into two daughter cells which are different in size. At 90 -110 min, the zygotes finish the second cleavage and form four daughter cells.