中国五种高山锄足蟾的核型、Ag-NORs和C-带的研究

作者用核型、Ag-NORs和C-带,对分布于川、滇两省的二属(齿突蟾、齿蟾)五种(胸腺齿突蟾、圆疣齿突蟾、凉北齿蟾、秉志齿蟾、疣刺齿蟾)锄足蟾作了属间和种间关系的比较分析,并讨论了它们的核型演化机制。结果表明:(1)齿突蟾和齿蟾两属间在核型和带型上都有明显的差异,演化途径主要的可能是含有重复DNA染色体片段的相互易位或臂间倒位;(2)属内不同种之间带型无显著差异,但某些对应染色体对间,其相对长度和臂比值差异明显,十分可能是常染色质片段的易位和臂间倒位所致;(3)凉北齿蟾有染色体数目变异多态现象;(4)五种锄足蟾均未发现异形性染色体。

STUDIES OF KARYOTYPES, AG-NORs AND C-BANDING ON FIVE MOUNTAIN PELOBATOID TOADS FROM CHINA

The karyotypes, C-banding and Ag-NORs of five Chinese pelobatoid toads (i.e Scutiger glandulatus, S. tuberculatus, Oreolalax liangbeiensis, O. pingii, O. rugosus) collected from Sichuan and Yunnan provinces were reported in this paper. The diploid number and karyotypic formulae of above mentioned species are same, being 2n = 26, 6 + 7. Similarly there is only one pair Ag-NORs in these species. But the differences of karyotypic compoments and banding pattern existed between two genera of Scutiger and Oreolalax. The former be possessed of one pair ST(No. 5) and 2p Ag-NORs (secondary constriction), whereas the latter was no ST only SM and 6q Ag-NORs. Therefore the reciprocal translocation containing the repeated DNA or constitutive heterochromatin and pericentric inversion may be their karyotypic change mechanisms. The C-banding positive staining mainly located the centromeres of all chromosomes in five species here. But the 6q strong stain appeared in Oreolalax species. The relative length and the location of centromere of some corresponding chromosome pairs between the species for each studied geaus are different in various degree. So the reciprocal translocation and pericentric inversion probably are the way of karyotype evolution. It is interesting to find the polymorphism of diploid number for 0. liangbeiensis, 2n=26 or 2n = 28. No heteromor-phic sex chromosome to be discovered for these five pelobatoid species using the karyotype and above mentioned banding methods.