6-DMAP诱导栉孔扇贝三倍体的细胞学观察

Cytological observation on triploid induction with 6-DMAP treatment in Chlamys farreri

用Bouin氏液固定、连续石蜡切片方法,对6-二甲基氨基嘌呤(简称6-DMAP)抑制第二极体诱导栉孔扇贝三倍体在受精和早期卵裂过程中的细胞学变化进行了详细观察。结果表明,在授精后25min,以60mg/L的6-DMAP处理栉孔扇贝受精卵15min,有效地破坏了纺锤体结构的形成,抑制了第2次减数分裂进程,致使受精卵内形成两种核相:一种是1个大的二倍性雌核和1个雄核;另一种是两个单倍性的雌核和1个雄核。不论形成几个雌原核,它们都能与雄原核相互靠近,在卵轴中央核膜逐渐发生融合,形成合子核,三倍体的合子核在卵内所占体积明显较二倍体的大。继而,合子核经过DNA复制,最后凝缩成染色体,发生有丝分裂,其过程与正常二倍体相同。

Induction of triploid in Chlamys farreri was implemented by inhibiting the second polar body of the fertilized eggs with 6-Dimethylaminopurine （6-DMAP）. Then the cytological changes of triploid in the process of fertilization and early cleavage was observed particularly under an optical microscope, with the samples in different developmental stages being fixed and sectioned continuously. The results revealed that the treatment with 60mg/L 6-DMAP for 15min could effectively destroy the forming of spindle structure and inhibit the course of meiosis 11 , resulting in forming two kinds of nuclear phase in the fertilized eggs, one was big diploid female pronucleus with one male pronucleus, the other one was two haploid female pronuclei with one male pronucleus. Regardless of how many female pronucleus formed, the female and male pronuclei of triploid eggs approached each other step by step and finally fused into zygotonuceus in the center of egg. The zygotonuceus volume of triploid in egg was evidently bigger than that of diploid zygotonuceus, for the former was higher in DNA content. After the completion of DNA copy, the chromatin of zygotonuceus condensed into chromosomes and then underwent mitosis, which was basically identical to the process of normal diploid.