云南三种齿蟾的细胞遗传学研究(锄足蟾科Pelobatidae,无尾目Anura)

CYTOGENETIC STUDY ON THREE OREOLALAX PELOBATOIDES FROM YUNNAN

本文报道了分布在云南的3种齿蟾(乡城齿蟾、景东齿蟾和棘疣齿蟾)的核型、Ag-NORs和C-带,结果表明2n=26(6+7).NF=52,一对次缢痕和Ag-NORs位于6 q,该区域同时被C-带正染,其余C-带位于各对染色体的着丝点区域。这些特征表现出3种齿蟾的核型同源性和原始性。齿蟾属内种间各对应染色体对在相对长度和臂比值的差异显著性测定表明其核型演化途径可能是臂间倒位和相互易位。3种齿蟾具有染色体数目和Ag-NORs的变异和异形现象,其中乡城齿蟾的一个多余染色体呈现C-带正染,因此可能是B染色体,是锄足蟾科中首次报道。三种齿蟾均未发现与性别相关的异形染色体。

The karyotypes, C-banding and Ag-NORs on three oreolalax pelobatoides (Oreolalax xiangchengensis, O. jingdongensis, O. granulosus) from Yunnan Province have been studied. The results demonstrated that these species have 2n=26(6+7), NF=52, and all components consisted of M or SM but not T. One pair of Ag-NORs located on 6q, which showed C-positive staining also, and the others are on the centromeric regions. These characteristics above described signified the homogeneity and primitive property of karyotype. The difference of relative lengths and arm ratio on their corresponding chromosomal pairs had been determined using the t value. It is inferred that the pericentic inversion and reciprocal translocation occured in the karyotypic evolution. The variation of chromosome number appeared in three species but the one additional chromosome of O. xiangchengensis showed the positive C-staining. From that it may be a supernumerrary chromosome (B chromosome). There are Ag-NORs and secondary constriction heteromorphism for them.Finally no heteromorphic chromosomes related with sexuality had been discovered using the coventional karyotype and above banding techniques.