Chromosome differentiation of four 2n = 50 chromosomal forms of Turkish mole rat, Nannospalax nehringi.

Nannospalax is a genus of blind rodents adapted to living in underground. The species have numerous chromosomal forms in Turkey, and their taxonomic position is still unknown. In this study, 15 mole rats of four different 2n = 50 forms were used; C- and G- banding processes were applied; and a comparison was made accordingly. Karyological results showed that the 2n = 50S form is a new form for Turkish blind mole rats. 2n = 50S form is determined from Andirin (Kahramanmaraş) and has NF = 70. The 2n = 50W form, on the other hand, differs from the others with NF = 74 form. C-banding results showed that heterochromatin blocks of all 2n = 50 are different, while only the 2n = 50W form has telomeric heterochromatin blocks. G-banding results, however, displayed homologies and differences among the chromosomal forms. After comparison, we determined that Robertsonian fusion is an efficient force on chromosomal evolution in blind mole rats in Turkey, and that telomeric heterochromatin is a distinctive character for the 2n = 50W form. We suggest that the chromosomal changing mechanism should be independent from climatic peculiarities. These results support the theory that ancestral karyotype should have the largest distribution in a chromosomally variable species.