Cytogenetic studies of Hynobiidae (Urodela). IV. DNA replication bands (R-banding) in the genus Hynobius and the banding karyotype of Hynobius nigrescens Stejneger.

The R-banding technique of Dutrillaux et al. (1973) was modified in order to analyze the chromosomes of salamanders in the genus Hynobius. Embryonic cells of Hynobius nigrescens Stejneger from Nakakubiki County, Niigata Prefecture, and Hakui County, Ishikawa Prefecture, were cultured in medium containing 5-bromodeoxyuridine (BrdU). Banded metaphases were obtained by the FPG (fluorescent-plus-Giemsa) technique (Perry and Wolff, 1974), with slight modifications. With this modified R-banding technique, multiple, clear DNA replication bands were obtained on the chromosomes, and 18 of 28 chromosome pairs could be identified easily by their replication patterns in embryos collected from Nakakubiki County. A distinct heteromorphism in banding pattern was detected on the long arm of chromosome 9 in these embryos, but the frequency of this variant was too low for chromosome 9 to be a sex chromosome. Chromosomes 1-14, except for 6, 12 (for which the data were not satisfactory), and 9 (the variant type from Nakakubiki County), had the same replication patterns in embryos obtained from Nakakubiki and Hakui Counties.