In this paper, we analyzed B chromosome variation in Korean field mouse Apodemus peninsulae Thomas 1907 (Rodentia, Muridae) based on a 40-year study of karyotypes collected from geographically distant populations in East Siberia, North Mongolia, China, the Russian Far East, and Japan (Hokkaido). We developed the database of individual variants of B chromosome systems in A. peninsulae. In Siberian populations all animals had Bs. The karyotypes of the studied animals contain from 1 to 30 Вs differing in size and morphology. Analysis of B chromosome systems in 598 individuals from different localities of the range shows the presence of 286 variants of Вs combinations in these animals. Unique sets of B morphotypes make up most of these variants (64.7 ± 1.3%), probably suggesting that individual Bs systems normally result from stochastic processes in the populations. The proportion of animals with a large number of Bs gradually decreases, probably due to increased complexities in the inheritance of large numbers of Bs. A. peninsulae is thus proposed as a good model for studying the origin and evolution of extra elements in the karyotype.

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Citation: Borisov YM, Abramov SA, Borisova MY, Zhigarev IA (2020) The occurrence of dot-like micro B chromosomes in Korean field mice Apodemus peninsulae from the shore of the Teletskoye Lake (Altai Mountains). Comparative AbstractThe data on the changes in the cytogenetic structure of the geographic population of Korean field mouse Apodemus (Alsomys) peninsulae Thomas, 1907 at the southern shore of the Teletskoye Lake (Altai Republic) are presented. In 1980 no dot-like microchromosomes were found in 34 mice captured on the southern and northern coasts of the Teletskoye Lake. In 2011, a 1.6-fold (from 2.7 to 4.3) increase in the mean number of B chromosomes compared to the rate estimated there earlier in 1980 was discovered. In 11 of the 15 mice (73%) captured in 2011, the karyotypes contained 1-2 dot-like micro B chromosomes and 1-5 macro B chromosomes. The pollution of the territory by the remains of the rocket fuel components may be an appropriate explanation for the cause of the karyological changes observed in A. peninsulae in this region.

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