云南三种角蟾的细胞遗传学研究

本文研究了云南三种角蟾的核型，C－带和Ag-NORs，结果显示宽头大角蟾，其2n=26(16M 8SM 2T),NF=50,5 8,No.10为T，次缢痕和Ag－NORs位于1p per，该区域同时还呈现C－带正染，其全部染色体的着丝点都有强弱不等的C－带染色；大花角蟾的核型2n=26(16M 8SM=2ST)，NF＝50，5＋8，No.6为ST，次缢痕和Ag-NORs位于5q pes，全部着丝点均有C－带正染；凹顶角蟾5n=26(16M 4SM 6T),NF=46,6 7.No.11-13为T，次缢痕和Ag-NORs位于5q per，全部着丝点及周围均有浓C－带正染。三个种均未发现与性别相关的异形染色体，最后讨论了角蟾属核型演化的途径。

A Cytogenetic Study of Three Megophrys Species from Yunnan Province

The karyotypes, Obanding and Ag-NORs of three Megopkrys toad from Yunnan Province have been studied. The results demonstrated that Megophrus carinensis has 2n = 26(16M + 8SM+2T), NF = 50, 5 + 8(karyotypic formulae) and its No. 10 is T. Its secondary constrictions (SC) and Ag-NORs having heteromorphic phenomenon located on lp per where C-positive staining was observed. Significant difference of the karyotypes and Ag-NORs between two populations from different distributed regions were found. M. giganticus has 2n = 26(16M + 8SM + 2ST), NF = 50,5 + 8, and No. 6 is ST. The SC and Ag-NORs are on 5q per. In some metaphases for such species the number of chromosome is 27, the additional one without distinct centromere is C-negative reaction. M. parva has 2n = 26(16M + 4SM + 6T) ,NF = 46, 6 + 7, No. 11-13 are T. The SC and Ag-NORs also locate on 5q per. All the centromeric regions of the chromosomes for three studied species showed the various degree staining of C-positive and the third species is darker than others. According to known data it was deduced that there exist reciprocal translocation and pericentric inversion in their karyotypic evolution.Finally no heteromorphic chromosomes related with sexuelity were discovered in the three studied species.