Comparative cytogenetics of Chinese and Japanese raccoon dogs, Nyctereutes procyonoides.

We investigated the relationships between subspecies of Nyctereutes procyonoides from China (2n = 54 + B chromosomes) and Japan (2n = 38 + B chromosomes). The chromosomes of Chinese and Japanese raccoon dogs were compared by means of conventional staining, G- and C-banding, and silver nitrate staining of NORs. Extensive G-banding homologies revealed karyotype evolution through chromosomal fusion. We believe the reduced diploid number in the Japanese raccoon dogs was achieved by fusion of 16 acrocentrics to form eight metacentric and submetacentric elements. Ten pairs of autosomes appeared to be identical in these subspecies and were presumed to have occurred as such in a common ancestor. G-band patterns of the sex chromosomes were similar in the two subspecies, but differences were noted with other banding and staining techniques. B chromosomes were present in varying numbers and sizes in all animals examined, but the morphology of the B chromosomes differed in the two subspecies. It was concluded from chromosomal and paleontological evidence that the two subspecies were derived from a common mainland ancestor and that the Japanese raccoon dogs is a relatively recent form.