Geographical variations in chromosomes of the greater Japanese shrew-mole,Urotrichus talpoides (Mammalia : Insectivora)

Karyotypes of the greater Japanese shrew-mole, Urotrichus talpoides (Talpid ae), collected from 57 localities in Japan were studied by conventional, G- and C-band staining techniques to elucidate geographical chromosomal varia tions, the mechanism of changes in chromosomes, and the distribution patter ns of karyotypic races. Shrew-mole samples examined could be divided geogra phically into two slightly divergent chromosomal forms designated as the we stern and eastern races. These two karyotypic races had the same diploid nu mber (34) and fundamental number (64), but they had autosomes with differen t makeups. A comparison of conventional karyotypes showed a distinct intras pecific variation in shape of autosomal pair no. 14 which was classified as subtelocentric in the western race and as metacentric in the eastern race. G- and C-banding analyses revealed that karyotypic variation found in no. 14 pair was involved in pericentric inversion and quantitative changes in c onstitutive heterochromatin. Intraspecific and geographical variation in ch romosomes caused by such karyological events is rare and unique among membe rs of the family Talpidae examined so far. Furthermore, our results demonst rated that the clear boundary between the two parapatric karyotypic races w as actually located along the Kurobe-Fuji line in the central part of Honsh u, but not along the Owari-Tsuruga isthmian line previously postulated by T suchiya (1987, 1988). Zoogeographical implications of the boundary of parap atric distribution in U. talpoides are also discussed.