Chromosomal polymorphisms due to heterochromatin growth and pericentric inversions in white-bellied rat, Niviventer confucianus, from China.

Different cytogenetic techniques were used to analyze the chromosomes of white-bellied rat, Niviventer confucianus from Mt. Tai and Jinan, Shandong Province and Ningshan, Shaanxi Province of China. Shandong populations have 2n = 46 chromosomes with 4 metacentric, 2 subtelocentric, 16 telocentric pairs of autosomes and the submetacentric X and telocentric Y. The chromosomal arm number (NF) of the two populations was 56. Shaanxi population has 2n = 46 chromosomes with 4 metacentric, 1 submetacentric, 1 subtelocentric and 16 telocentric pairs of autosomes and the submetacentric X and telocentric Y. The karyotype of Ningshan population showed NF = 58. As the result of the comparison of C- and G-banding patterns, and compare with other species in the genus Niviventer, we suppose that the chromosomal evolution of Niviventer involved in pericentric inversion and heterochromatin growth. The submetacentric chromosomes of Shaanxi population would be originated from the growth of heterochromatin of the subtelocentric chromosome of Shandong population.