Abstract
The karyotype and G-, C- and N-banding patterns of the Japanese water shrew, Chimarrogale platycephak platycephala, have been examined for the first time. The karyotype is characterized by a diploid number of 52 and by an FN (fundamental number) of 100. The sex chromosomes are of the XX(_??_)-XY(_??_) type usual in mammals. The pair no. 1 carries a pronounced secondary constriction on the proximal region of its short arm which functions as a nucleolus organizer, as confirmed by AgI staining. No. 1 chromosomes are also noteworthy in that their short arms distal to the secondary constriction are totally heterochromatic and these arms are significantly different in their length, regardless of the sex, constituting a heteromorphic pair.
The phyletic relation between the Japanese water shrew and the European water shrew, which are included in different subfamilies in the present taxonomic system, has been discussed on the basis of their karyological similarity.
