Comparative Cytogenetics. 2009. 3(1): 1-9.
Chromosome polymorphism in Bulgarian populations of the striped field mouse (Apodemus agrarius Pallas 1771)
Chassovnikarova T., Atanasov N., Dimitrov H.
Abstract. Chromosome polymorphism in Bulgarian populations of the striped field mouse (Apodemus agrarius Pallas, 1771) has been described. The diploid chromosome number is 2n=48 (NFa = 54). In the karyotype of 3 specimens from the Iskar region, the presence of an additional B chromosome has been established for the first time. The autosomes are 19 acrocentric pairs, continuously decreasing in size, and 4 pairs of be-armed chromosomes, barely distinguishable by size and location of the centromere. Specimens with 3 pairs of metacentric chromosomes were firstly described in Bulgaria for the regions of Iskar and Omurtag. The localization of heterochromatin in the centromeric regions of the chromosomes, blocks of heterochromatin of different sizes, as well as intercalated bands, distinguishable in weakly spiraled chromosomes are found. Telomeric heterochromatin is present in the largest autosomal pair and in two of the middle–sized autosomal pairs. The largest and smallest pairs of be-armed chromosomes do not have centromeric heterochromatin, whereas all the other autosomal pairs do. The presence of a NOR in 6 chromosomal pairs is established. Two of the pairs exhibited pericentromeric NORs, whereas the other 4 displayed telomeric NORs. The karyotype analysis illustrates the chromosome and genome polymorphism of A. agrarius in Bulgarian populations.