CHROMOSOMAL VARIATION AND ABNORMAL KARYOTYPES IN THE RED-BACKED MOUSECLETHRIONOMYS RUFOCANUS (RODENTIA, MICROTINAE)

G-banding and C-banding of chromosomes were studied in populations of the red-backed mouse Clethrionomys rufocanus from 11 localities of eas tern Russia. Intrapopulation polymorphism of autosome 3 caused by the deletion-duplication of the short-arm heterochromatin (2n = 56; NFa = 56-58) was demonstrated. The karyotype of CI. rufocanus from continent al populations and Sakhalin Island was shown to have a large subteloce ntric chromosome of pair 3 (NFa = 58), whereas in the population from Kunashir Island, chromosomes of this pair were acrocentric (NFa = 56). One animal from the population of the Kedrovaya Pad' Reserve (Primors k krai) had a pericentric inversion (acrocentric morphology) of the Y chromosome. In two animals, a female from the Ussuriiskii Reserve (Pri morsk krai) and a male captured near the Tomari Settlement (Sakhalin I sland), a pericentric inversion of one chromosome of pair 6 was found (NFa = 59). The inversion detected in the animal from the Sakhalin pop ulation was accompanied by the loss of the centromeric heterochromatin . In contrast, the inversion of the chromosome pair 6, which was found in. the mouse from the Primorsk krai population, did not involve the loss of centromeric heterochromatin. Analysis of our results and data from the literature showed that the karyotype of Cl. rufocanus is not constant, as was thought earlier. The percentage of animals with abnor mal karyotype (1.6%) was higher than in other groups of red-backed mic e studied (0.12-0.7%).