[Unusually high number of B-chromosomes and mosaicism among them in the Asiatic forest mouse Apodemus peninsulae (Rodentia, Muridae)].

Karyological analysis of Apodemus peninsulae from Western Siberia was made. It was established that animals under study are characterized both by interindividual variation of B-chromosome number or polymorphism which was described previously and by intraindividual variation or mosaicism. Diploid numbers are 55-57, 58-61, 61-65 and 68-72, i. e. studied animals possess 3, 4, 5 and 5 cell clones, respectively. The highest number of B-chromosomes in mammals was found to be 24.