Banded karyotypes and the localization of ribosomal RNA genes of Eurasian flying squirrel,Pteromys volans orii(Mammalia, Rodentia)

SUMMARYKaryotypes of five males and four females of Eurasian (Siberian) flying squirrel, Pteromys volans orii, were analyzed with G-, C-, Ag-NOR staining methods. Fluorescence in situ hybridization (FISH) was applied to the location of 18S and 28S ribosomal RNA genes. The diploid chromosome number of this species was 2n = 38 with the arm number (NF) of 68. C-bands were located at the centromeric region of all chromosome pairs. Nucleolus organizer regions (NORs) appeared in the short arm of chromosome 17, and the location of Ag-NORs was indistinguishable from the site of the rRNA genes. The size variation of NORs was observed in each individual, indicating heteromorphism of NORs in this species.