Voles of the group Microtus arvalis (Rodentia, Cricetidae) in the Urals

Karyotypes of two sibling species from group Microtus arvalis in 6 sites of the Middle and Southern Urals have been described. Microtus arvalis was found in Shala (Sverdlovsk district), at the Eastern Urals Reserve (Chelyabinsk district) and in the vicinity of the Orenburg Reserve. M. rossiaemeridionalis inhabits southern part of Ekaterinburg district and western part of Orenburg district. In 1954-1957 in two radioactively polluted territories mutant specimens were found. In the vicinity of the Eastern Urals Reserve a female 45, XO and a heterozygote for the 5-th pair have been trapped, nearby the Totsky ground two of six trapped M. rossiaemeridionalis females possessed male chromosome constitution XY.