Toshijiro Kawamura

Aspects of the Reproductive Biology of Japanese Anurans

Seventeen anurans occur on the four main islands of Japan and on the Islands of Tsushima situated between Japan and Korea. Two of these, Rana nigromaculata and R. brevipoda, are pond frogs allied to Rana esculenta.1 Six other species, Rana japonica, R. ornativentris, R. tagoi, R. chensinensis, R. tsushimensis and R. dyboswkii, are brown frogs allied to Rana temporaria, although Rana tagoi differs from the others in many respects. In addition to these species, two small, dark-colored frogs, Rana rugosa and R. limnocharis, and a large American frog, Rana catesbeiana, are widely distributed in Japan. In other genera Hyla arborea japonica, Bufo bufo japonicus, Bufo torrenticola and three species of Rhacophorus occur. Although it is generally believed that Bombina orientalis occurs on Tsushima, no one has recently found it there. During the last ten years, we have made a number of studies of reproductive biology using most of the Japanese anurans and some foreign ones.

Karyotypes of Rana tagoi Okada with diploid number 28 in the Chausu Mountains of the Minamishinshu district of Nagano Prefecture, Japan (Anura: Ranidae)

Karyotypes of Tago’s brown frog Rana tagoi from the Chausu mountains in Minamishinshu of Nagano Prefecture were examined by conventional Giemsa staining, C-banding and late replication (LR)-banding. Chromosome number was 2n = 28 in all cases. The 28 chromosomes consisted of four pairs (1–4) of large biarmed chromosomes, two pairs (5–6) of telocentric chromosomes and eight pairs (7–14) of small biarmed chromosomes. Chromosome pair 11 had a secondary constriction on the long arm. In females, the C-band on the long arm of chromosome pair 6 was detected in both homologs, but was absent from the arms of the homologs of chromosome pairs 5 and 9. In males, C-bands were found in the long arms of both homologs of chromosome pairs 5 and 6, were present only in one homolog of chromosome pair 5 for certain male specimens and found in only one homolog of chromosome pair 9. Specimens of R. tagoi (2n = 28) should thus have two pairs of telocentric chromosomes to provide the same number of chromosome arms, these originating quite likely from chromosome pair 1 in the 26-chromosome specimens by centric fission. Heteromorphic sex chromosomes of the XX-XY type in R. tagoi (2n = 28) in the Chausu mountains were identified. Karyotypes of tail-tip cells from a hybrid tadpole between female R. tagoi (2n = 26) from the Hinohara village in Tokyo and male R. tagoi (2n = 28) from the Chausu mountain population were examined by squash preparation. Chromosome number was 2n = 27 in all tadpoles. The 27 chromosomes consisted of one chromosome set of R. tagoi (2n = 28) and one of R. tagoi (2n = 26).