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SUMMARY
Karyotypes of Rana narina, R. ishikawae, R. subaspera, R. holsti, R. okinavana, and R. namiyei were analyzed by making use of chromosomes from bone marrow cells. The first five species have 13 pairs of chromosomes, of which five pairs (Nos. 1–5) are large and eight pairs (Nos. 6–13) are small. Number 1 is metacentric, Nos. 3, 8 and 11 are subtelocentric, and the others are submetacentric. Number 9 has a secondary constriction on the long arm. Number 4 of R. subaspera and R. holsti has an additional secondary constriction on the long arm. Differing from these species, R. namtyei has 11 pairs of chromosomes that are not readily separated into different size groups, which is unique in the family Ranidae. All pairs of chromosomes of R. namiyei are submetacentric and none has a secondary constriction.
The karyotypes of R. narina, R. ishikawae, R. subaspera, and R. holsti resemble one another, suggesting a common origin. Comparisons with karyotypes of other species of Rana suggest that these species have become differentiated in external morphology without large changes in the ancestral karyotype. The karyotype of R. okinavana differs from those of the above four species and probably from those of the allied forms of Japan and Taiwan. The karyotype of R. namiyei is decidedly different from that of all other species of ranids and thus R. namiyei should be separated taxonomically from all other ranids at the subgeneric rank.
