A comparative chromosome study by means of G-, C-, and NOR-bandings of the weasel, the pygmy weasel and the stoat (Mustela, Carnivora, Mammalia)

The karyotypes of 9 weasels (Mustela nivalis vulgaris), 7 pygmy weasels (M. n. nivalis) and 11 stoats (M. erminea) were studied. G-, C- and NOR-banding revealed distinct similarities between the species/subspecies. The two weasel forms have 2n=42 and identical karyotypes, the stoat has 2n=44. The weasel karyotypes differ from the karyotype of the stoat by one centric fusion and by the addition of large blocks of constitutive heterochromatin to the short arms of 7 chromosome pairs. Only one chromosome pair in each species has a nucleolar organizing region. One weasel and one stoat had aberrant karyotypes. The weasel had extra chromosome material of unknown origin added to one chromosome, the stoat had 2n=43 due to centric fusion of two t chromosomes. The species problem in Scandinavian weasels and karyotype evolution in the Mustelinae are discussed.