两种髭蟾的Ag—NORs,C—带及核型的研究

本文叙述和比较了峨眉髭蟾和哀牢髭蟾的核型,C-带和Ag-NORs,结果表明两者有下列相同方面:2n=26(6+7)、除No.3为SM外,其余诸对概为M,次缢痕和Ag-NoRs位于6q,并都表现出异形现象,No.1长臂有长度异形,但所增染色体片断不呈现C-带正染,C-带正染主要是在各对染色体的着丝点区域,另外No.2短臂近着丝区域亦为正染。这些表明二者之间有很大的核带型同源性。但是二者间在核型的某些对应染色体之间,在相对长度(6对)和臂比值(2对)方面有显著性差异,故可推测其机制是相互易位和臂间倒位。另外,哀牢髭蟾未发现与性别相关的异形性染色体。

A Study of the Karyotype, C-banding and Ag-NORs on Two Vib- rissaphora Toad Species (Pelobatidae, Anura)

The karyotype, C-banding and Ag-NORs of two vibrissaphora species (Vibrissaphora bo-ringii and V. ailaonica) have been studied in present paper. It was found that they all had 13 pairs chromosomes (2n = 26, 6 + 7), of them only No.3 is SM, while all the rest are M, so NF = 52. Their secondary constriction and Ag-NORs located on 6q and showed the hetermor-phisms. The length of long arm of No. 1 chromosome had the heteromorphism, too, but the additional segment was negative C-staining. The positive C-stanirig mainly located on the centromeres of all chromosomes, also on the short arm near the centromere of No.2. These facts as mentioned above showed the karyotypic homologue between two examined species. The unstable C-staining occasionally appeared on 3q, 6q and 13q. We have compared the relative length and arm ratio of each corresponding pair of chromosome between the two examined species and determined the significant difference of the means. The results indicated that the relative length of Nos. 3,5,7,8,11,13 and arm ratio of Nos. 8,9 had significant difference. Therefore the reciprocal translocation and pericentric inversion may be their mechanism of karyotypic evolution. Finally the sexual dimorphism of the chromosomes was not detected in somatic karyotypes of male and female Vibrissaphora ailaonica.