A coparative study on karyptypes and chromosome banding pattern of three odor frogs of Rana

The chromosomes of three odor frogs, Luetuosae-group of Rana were analyzed by conventional, as well as C-banding and silver staining techniques. The three species here examined all had 26-chromosome karyotypes encompassing 5 large and 8 small homologous pairs. Differences among them were found in gross shapes of chromosomes and positions of secondary constrictions. Generally speaking, karyotypes of R.andersonii and R.grahami resembled each other, while the karyotype of R.tiannanensis differen from the former two in several respects.Analyses of karyotypes by C-banding technique indicated that, centromeric areas of every chromosome and interstitial parts of some chromosomes of each species were hetero-chromatinized, and differences of distribution of heterochromatin were found among species. In early metaphase plates of R.andersonii, much more heterochromatinized areas were observed, and when it reached late metaphase, the numbers of heterochromatin sections in each chromosome pair reduced to a limited level, e.g. centromeres and a few intersititial parts.The active nucleolar organizer regions (NORs) were localized in long arms of pair No. 10, in connection with secondary constrictions for R.andersonii and R.grahami as in other odor frogs previously reported,but in the long arm of pair No. 6 for R. tiannanensis. The cytogenetic and taxonomic implications of the findings were discussed based on comparisons with each other, and with published leterature.