Evidence for heteromorphic sex chromosomes in males of Rana tagoi and Ranasakuraii in Nishitama district of Tokyo (Anura : Ranidae)

Karyotypes of the Tago brown frog Rana tagoi and stream Tago brown frog Ran a sakumii from a mountain region in the Nishitama district in Tokyo were ex amined by conventional Giemsa staining, C-banding and late replication (LR) -banding. Chromosome number was 2n = 26 in all cases. The 26 chromosomes co nsisted of five (1-5) pairs of large chromosomes and eight (6-13) pairs of small chromosomes. Chromosome 10 had a secondary constriction on the long a rm. In all frogs, on chromosome pair 8, the XX/XY type sex chromosome was p resent. C-banding analysis indicated that, in R. sakuraii, neither the X no r Y chromosome possessed interstitial C-bands but each had centromere stain ing, while in R. tagoi, an interstitial C-band was present on the long arm of the X chromosome. The Y chromosome had no interstitial C-band. LR-bandin g analysis demonstrated the X and Y chromosomes to have a LR-band on the sh ort arm and two LR-bands, each on the long arm, and the bands on both speci es to be essentially the same. Heteromorphic sex chromosomes in males of R. sakuraii and R. tagoi were identified for the first time in this study.