Abstract
The chromosomes of Japanese brown frogs Rana japonica and R. ornativentris were analyzed with conventional Giemsa staining, C-banding for heterochromatin distribution, and silver staining for nucleolus organizer regions (NORs). R. japonica had 2n=26 chromosomes, centromeric heterochromatin on all chromosome pairs, and NORs on the secondary constrictions on a long arm of No. 9 chromosome. R. ornativentris had 2n=24 chromosomes, pericentric heterochromatin on 5 large chromosomes, and NORs situated in the secondary constrictions of a long arm in No. 10 chromosome. According to the banding karyotype analyses of both species, the process and possible consequences of chromosome number reduction from an ancestral 26-chromosome karyotype is discussed.
