B Chromosomes of Korean Mice ( Apodemus peninsulae Thomas, 1907 (Rodentia, Muridae)) on the Eastern Slopes of the Qingha
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AL GENETICS
B Chromosomes of Korean Mice (Apodemus peninsulae Thomas, 1907 (Rodentia, Muridae)) on the Eastern Slopes of the Qinghai-Tibet Plateau (China) Yu. M. Borisova, I. A. Zhigarevb, *, and B. I. Sheftela, ** aSevertsov
Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, 119071 Russia b Moscow Pedagogical State University, Moscow, 129164 Russia *e-mail: [email protected] **e-mail: [email protected] Received November 10, 2019; revised December 12, 2019; accepted January 14, 2020
Abstract—Chromosome sets of eight Apodemus peninsulae individuals captured in Gansu Province (Lianhuashan Natural Reserve) were studied for the first time in 2012. Chromosome sets of mice contained from 55 to 62 chromosomes and included 48 A chromosomes and 7–14 additional B chromosomes of different morphologies. Keywords: karyotype, B chromosomes, Apodemus peninsulae, Qinghai-Tibetan Plateau DOI: 10.1134/S1022795420090033
INTRODUCTION Additional chromosomes (B chromosomes) are currently discovered in many species of not only animals but also plants and fungi. In mammals, they are observed in 55 species. Most of them belong to the order of rodents (Rodentia). For example, out of 20 species of mice of the genus Apodemus, additional B chromosomes were detected in six [1]. One of them is the East Asian or Korean mouse (A. peninsulae). To date, the karyotype of representatives of this species from many regions in the north of the range, mainly within Russia, as well as Japan, Korea, and Mongolia, has been well studied. In virtually all of those A. peninsulae examined to date, additional chromosomes are noted in individual karyotypes; exceptions are rare [2]. They have different shapes and numbers: their number can reach up to 30 (as a result, these individuals have 78 chromosomes in the karyotype). There is a single population known to live on Sakhalin Island the animals of which do not have B chromosomes in the karyotype [3]; however, in another island population, on Hokkaido Island, they are present [4]. The largest number of B chromosomes was detected in mice living in Siberia [2, 3, 5–7]. Cytogeneticists have a special interest in this species owing to its karyological uniqueness, since it is characterized by some rare features. These include the presence of the highest and most diverse number of B chromosomes among mammals (it varies from 0 to 30); a sharp morphological difference between the A chromosomes (one-armed) and B chromosomes
(often two-armed); the presence in the system of B chromosomes of this species of various size-morphological variants (in size, from point to large; in morphology, from micro chromosomes, with an unclear centromere position, to two-arm macro B chromosomes); and the existence of three types of variation on B chromosomes: interpopulation, interindividual, and within the individual (mosaicism). These provisions determine the prospects of using East Asian mice as a model object in the study of the phenomenon of B chromosomes in mammalian karyotypes. This will help clarify the
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