Cytogenetical studies on insectivora. II. Geographical variation of chromosomes in the house shrew, Suncus murinus (soricidae), in east, southeast and southwest asia, with a note on the karyotype evolution and distribution.

Abstract

Karyotypes of the house shrew (Suncus murinus) collected from 8 different localities in East, Southeast and Southwest Asia were examined with an interest of the geographical variation and distribution of this animal. Specimens collected from 7 localities in Japan, Indonesia and India had always 40 chromosomes (basic type), with apparent geographical variations in the size and shape of the Y chromosome. Specimens collected from Sri Lanka, on the other hand, had 32 chromosomes, among which 4 pairs were large metacentrics, probably derived from the Robertsonian fusion of 8 acrocentric pairs in the basic karyotype. Referring to the present and other studies, it is suggested that the house shrews with 40 chromosomes should have distributed originally in India, and then migrated to Southwest, Southeast and East Asia. The chromosome number reduction could have occurred in the animals moved to southern India and then they migrated to Sri Lanka. Mechanism of the karyotype evolution in the house shrew is discussed in relation to the environmental mutagens.