Abstract
The karyotypes of two closely related species of mustelids, the Japanese ermine (Mustela erminea nippon) and the least weasel (M, nivalis namiyei), were compared by means of the G-and C-banding methods. A high degree of G-band homology was observed between the chromosome arms of the two species, except for the faintly stained (G-negative) regions in the short arms of the pairs Nos. 1 to 5 of the least weasel (W1 to W5). These G-negative regions were found to correspond to the deeply stained C-heterochromatin, as reported previously (Obara 1982, 1984). The present results confirmed the previous notion that the karyotype of the least weasel has derived from the ancestral one similar to that found in the ermine mainly through duplication of C-heterochromatin, Robertsonian fusion and tandem translocation.
