静水压休克诱导水晶彩鲫三倍体和四倍体的细胞学机理初探

PRELIMINARY STUDY ON THE CYTOLOGICAL MECHA- NISM OF TRIPLOIDY AND TETRAPLOIDY INDUCED BY HYDROSTATIC PRESSURE SHOCK IN TRA- NSPARENT COLORED CRUCIAN CARP

本文分析了静水压休克诱导水晶彩鲫三倍体和四倍体的细胞学机理，促使第二极体保留的压力敏感期较短，在卵子第二次成熟分裂中后期的某段时间，也就是受精后４－５ｍｉｎ时；而在这之前，为卵子启动期，施加压力会破坏卵子的激动和修整过程，造成发育受阻；其后，为压力不应期，此时第二次成熟分裂态势也趋明朗，压力对保留第二极体失去作用。本文还对促使第二极体保留生产鱼类三倍体和抑制第一次卵裂诱导鱼类四倍体的条件等问题进行了讨论。

The cytological mechanism of triploiody and tetraploidy induced by hydrostaticpressure shock was analysed through histological sectoion techniques in transparentcolored variety,Crucian carp the major effects of hydrostatic pressure treatmentare to destruct spindle and intefere chromosome movement so that triploids andtetraploids are induced becauseof the retention of the second polar body andblocking of the first cleavage。The sensitive period for inducing second polar body retention is short and is atthe metaphase and anaphase of meiotic division II,i.0。4- 5min after sperm- eggfertilization, Before this period,the fertilized eggs are in the initializing stage。Hydrostatic pressure treatment of this stage would disrupt the exciting and decorat- ing process of fetilized eggs,hindering embryo development.After the sensitive periodthe tendency of second meiotic division is so strong that application of hydrostaticpressure fails to control and retain second polar body.The stage is the nonsensitiveperiod。Fertilized eggs of transparent colored crucian carp were shown to develop intometaphase of first mitosis at 50- 52min after fertilization,into anaphase at 52-57min and into telophase at 57 min(water temperature 14一16℃).The effective pe-riod for inhibiting first mitosis for inducing tetraploidy by hydrostatic pressure wasfound to be during the metaphase and anaphase of first cleavage。Hydrostatic pres-sure treatment not only produced reversible microtubule depolymerization,damagedthe spindle and arrested the process of first mitosi8,but also resulted in chromoso-me condensation to various extents.Tripolar spindle bodies were observed in sometreated fertilized eggs.These phenomena,especially formation of tripolar spindlebody,might be related to chromosome breakage and loss in the induction of tetra-ploidy.It is these changes of mitotic apparatus that resulted in a large number ofaneuploids。Based on the cytological mechanism of triploidy and tetraploidy induction,adiscussion was made on the conditions for the prevention of second body extrusionfor producing triploids,and on the conditions for the inhibition of first cleavagefor inducing tetraploidy。