Cytogenetic studies of Hynobiidae (Urodela)

Chromosome analysis was done in salamanders belonging to the genus Hynobius using the R-banding (RBG) technique. The embryonic cells of H. leechii Boulenger from Korea and H. nebulosus (Schlegel), H. tokyoensis Tago, H. nigrescens Stejneger, and H. retardatus Dunn from Japan were cultured in medium containing 5-bromodeoxyuridine. R-banding patterns in these five species were analyzed, except for most of the small-sized chromosomes. Eighteen out of 28 chromosome pairs in H. leechii, H. nebulosus, H. tokyoensis, and H. nigrescens, and 16 out of 20 chromosome pairs in H. retardatus could be identified by their R-banding patterns. The R-banding patterns in H. leechii, H. nebulosus, H. tokyoensis, and H. nigrescens were very similar to one another as are their karyotypes. Among these four species, about 90% of the total lengths of the karyotypes in each species showed homoeologous R-banding patterns, while among all the five species, including H. retardatus, homoeologies decreased to about 65%. The results imply that H. leechii, H. nebulosus, H. tokyoensis, and H. nigrescens are extremely close to one another phylogenetically, and that H. retardatus is a near phylogenetic relation to the other species of this study.