用6-DMAP诱导栉孔扇贝异精雌核发育四倍体的细胞学观察

Cytological observations of early development of allogynogenetic tetraploid induced by 6-DMAP in scallop Chlamys farreri

用6-二甲基氨基嘌呤(6-DMAP)抑制受精卵第一极体和第二极体的排出,诱导栉孔扇贝Chla-mys farreri异精雌核发育四倍体。采用石蜡切片法,在光学显微镜下观察受精卵在受精和早期卵裂过程中细胞学的变化。结果显示:被遗传灭活的长牡蛎Crassostrea gigas精子(照射强度1 500μW/cm2,照射时间60 s)能够与栉孔扇贝卵子正常授精并激发受精活动,但受精卵发育速度较对照组的迟缓;受精卵即将排出第一极体之前用6-DMAP(终浓度50 mg/L)处理35 m in,抑制受精卵第一极体和第二极体的排出;至原核形成期,四倍性雌核最终融合,在此过程中精核一直处于凝缩状态,不解凝,不形成雄性原核;到第一次卵裂前期,精核以致密的染色质体(DCB)形式位于两组母本染色体之间,卵裂末期,精核位于两卵裂球之间的卵裂沟上或进入其中一个卵裂球的细胞质中;第二次卵裂过程中,精核仍然以DCB形式滞留于卵裂沟上或其中一个卵裂球中。另外,作者还观察到核物质分离紊乱、染色体多极分离等现象,并对产生这种现象的原因进行了探讨。

This paper deals with the induction of allogynogenetic tetraploidy conducted by 6 - DMAP via blocking the release of the first and the second polar bodies in the fertilized eggs in scallop Chlamys farreri. The eggs were fertilized with genetically inactivated Pacific oyster Crassostrea gigas sperm（ 1 500 μW/cm^2, 60 s）by ultraviolet radiation（UV） and 6 - DMAP at a final concentration of 50 mg/L just before the first polar body expel from the eggs. Results showed that UV inactivated Pacific oyster sperm inseminated the scallop eggs and activated the fertilization process even though the development was delayed. By the time the pronucleus formation, the tetraploidy female pronuclei finally fused. Before the first cleavage completed, the sperm nucleus became a dense chromatin body （DCB）, which did not participate in the karyokinesis and located between the two sets of maternal chromosomes. After completion of the first cleavage, DCB was observed either in the region of the first cleavage furrow or in the cytoplasm of one of the two blastomeres. During the second cleavage, the sperm nucleus were still maintained in the situation of DCB and maintained at the similar positions. In addition, the embryos with irregular division of nuclear materials and chromosome pluripolar segragation were also observed in this experiment. The reasons for irregular division of nuclear materials and chromosome pluripolar segragation were discussed in this paper.