点带石斑鱼的核型、C带、Ag-NORs

The karyotypes,C-bands patterns and Ag-NORs of Epinephelus malabaricus

采用PHA活体注射结合秋水仙素培养,取点带石斑鱼全肾,低渗处理,空气干燥制片法制作染色体标本,对染色体进行Giemsa染色、C带及Ag NORs等系列研究。结果表明:(1)点带石斑鱼2n=48,核型组成为48t,NF=48,没有异型性染色体分化;(2)在最小一对染色体的着丝粒与其染色体臂之间,靠近着丝粒部位有明显的次缢痕;(3)在间期核中,通过银染表现出核仁的数目为1～4个,1个核仁的间期核数目最高,多达55%,4个核仁的间期核数目占2%;(4)50%有丝分裂中期相能观察到Ag NORs,Ag NORs主要出现在第24对同源染色体上,第5对同源染色体也可观察到,但其它染色体上则没有;(5)Ag NORs的数目在不同的细胞中表现出多态性,数目为1～4个,出现4个Ag NORs的频率最低(6.8%),出现2个Ag NORs的频率最高(58.1%);(6)第24对同源染色体近着丝粒的臂内具次缢痕,是Ag NORs所在的区域,该区域分布有大量的结构异染色质,即Ag NORs与C带强阳性呈现严格的同步对应;(7)点带石斑鱼所有染色体着丝粒为阳性C带,而且第24对染色体几乎整个染色体臂都呈C带阳性,着色强度与该对染色体上的着丝粒C带相同。最后讨论了核型演化规律和Ag NORs、C带的发生机制。

The chromosome specimens of Epinephelus malabaricus (Bloch & Schneider)were obtained from metaphase of kidney cell by viv-injection of PHA and cultivation of colchicines, hypatoic-air drying technique,and then by studying their Giemsa stain,C-bands and Ag-NORs.The results were as follows: 1)E.malabaricus had a diploid chromosome number of 48 and its karyotype formula was 48t, NF=48,sex chromosome was not found;2)There was a pair of chromosomes with secondary constriction close to the centromere of chromosome t 24; 3)1-4 nucleoli appeared in the nucleus of interphase,55%nuclei had l nucleolus and only 2%for 4 nucleoli;4)Ag-NORs appeared in the chromosome t 24 of 50%metaphase,sometimes in the chromosome t5,but not in other chromosomes;5)The Ag-NORs polymorphisms were individually specific,1-4 pairs of the number,and the frequency of 4 Ag-NORs were lowest;6)The secondary constrictions and positive C-bands were coincident,close to the centromere of the chromosome,and mass constrictive heterochromatins appeared in that region;7)All the centromeres of chromosomes were darkly stained C-bands,and the whole arm of chromosome t 24 and its centromere were same positive C-bands.8)The evolutive regulation of the karyotype and the developing mechanism of Ag-NORs and C-bands were discussed.