Heterochromatin distribution and nucleolar organizer regions (NORs) in chromosomes of the Taurus ground squirrel, Spermophilus taurensis Gunduz et al., 2007 (Mammalia: Rodentia), in Turkey

The distribution of C-heterochromatin blocks and nucleolar organizer regions (NORs) in the Taurus ground squirrel from Turkey was studied. The karyotype of Spermophilus taurensis comprised 40 chromosomes, the fundamental chromosome number (NF) was 80, and there were 76 autosomal arms (NFa). All autosomes and the X chromosome had pericentromeric C-heterochromatin, whereas the Y chromosome appeared to be entirely heterochromatic. NORs were observed in the terminal regions of the short arm of 2 pairs of submetacentric and 2 pairs of subtelocentric chromosomes. All the NORs were homomorphic and of medium size. The S. taurensis karyotype differs from that of S. xanthoprymnus by a low diploid number, by a C-positive Y chromosome, and by the number and localization of NORs. It was also determined that its Y chromosome resembles that of S. citellus, in terms of its heterochromatic nature.