Comparative cytogenetics of Chinese and Japanese raccoon dogs, <i>Nyctereutes procyonoide</i><i>s</i>

Abstract

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 dog 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 dog is a relatively recent form.

Overwintering strategy of wild free-ranging and enclosure-housed Japanese raccoon dogs (Nyctereutes procyonoides albus)

“…It has long been thought that the raccoon dog was unique among canids in that the overwintering strategy of the species involves hibernation, partial hibernation, or winter lethargy Kauhala and Saeki 2004;Ward and Wurster-Hill 1990;Ward et al 1987). Such assumptions were based on observations that this species accumulated extensive fat stores in autumn (Korhonen et al 1991), exhibited prolonged denning during winter (Ward and Wurster-Hill 1990) and was behaviorally torpid at this time (Kauhala and Saeki 2004), rather than on measurements of body temperature (T b ) or metabolic rate during winter denning.…”

Review

“…Despite the difference in the chromosome number, the G-banding technique revealed extensive homology. These results lead some authors to a conclusion that the ancestral canid karyotype was dog-like and that the centric and tandem fusions played the main role in the karyotype evolution in this family (YOSHIDA et al 1983;WARD et al 1987;GRAPHODATSKY et al 1995). On the other hand, TODD (1970) proposed that the ancestral karyotype was similar to that of the Japanese raccoon dog and the karyotypes with higher diploid numbers evolved by centric fission events.…”

“…The Y chromosome in both subspecies of the raccoon dog has a paracentromeric C-band on the q arm. The canine Y chromosome demonstrates a darkly stained long arm (PATHAK et al 1982;WARD et al 1987). …”

“…In the dog and raccoon dog NORs residue on three autosome pairs and on the Y chromosome. The following chromosome pairs of these species bear the NORs: 1, 4, 13 and Y in the Chinese raccoon dog (PIENKOWSKA and ZAGALSKA 2001) and 11, 12, 18 and Y in the Japanese raccoon dog (WARD et al 1987). The NORs in the canine karyotype were detected on two large autosomes (7 and 17), one small autosome and on the Y chromosome (MÄKINEN et al 1997;PIENKOWSKA and SWITONSKI 1998).…”

“…This high homology of chromosome arms is also shared by the foxes and the raccoon dog, since approximately 75% of chromosome arms of both foxes have homologous counterparts in the raccoon dog karyotype (WAYNE et al1987). In the karyotypes of the Japanese raccoon dog and the Chinese raccoon dog chromosome arm homologies were also studied by the comparison of banding patterns (WARD et al 1987). Despite the difference in the chromosome number, the G-banding technique revealed extensive homology.…”