Chromosomal polymorphism in the gray shrew Crocidura attenuata (Mammalia : Insectivora)

Abstract

Conventional and G-banded karyotypes of Crocidura attenuata Milne-Edwards, 1872 from Guangdong, southern China, are reported. The diploid chromosome number (2n) varied from 35 to 38among specimens, while the fundamental arm number (FN) consistently was 54. Of the autosomes, 14 pairs including four meta- or submetacentric, three subtelocentric, and seven acrocentric pairs showed no variation in all specimens,, whereas the remaining pairs showed Robertsonian polymorphism. The X and Y chromosomes were medium sized submetacentric and small acrocentric chromosomes, respectively. These karyotypes differ from that of C. attenuata from Taiwan, which has 40 chromosomes with 56 arms. Such differences are largely attributable to a non-Robertsonian rearrangement, where both 2n and FN values are different from each other. The largest metacentric pair observed in karyotypes from Guangdong may have resulted from the centromere-telomere translocation between an acrocentric and a subtelocentric pairs of karyotype homologous to that from Taiwan. Both morphometric difference and sequence divergence in mitochondrial cytochrome b gene between samples from Guangdong and Taiwan was relatively small. However, the nonRobertsonian rearrangement assumed between karyotypes of the shrews from Guangdong and Taiwan suggest that they are reproductively isolated from each other. The eastern continental and Taiwanese populations therefore may represent different species under the names, C. attenuata (sensu stricto), and C. tanakae Kuroda, 1938, respectively.