Cytogenetics of vesper mice, Calomys (Sigmodontinae): a new karyotype from the Puna region and its implication for chromosomal phylogeny.

The karyotype of specimens identified as Calomys lepidus, trapped at 3600 m above sea level in the Puna region, northwestern Argentina, was studied. All specimens analysed showed a 2n = 44 (NF(a) = 68) asymmetrical karyotype with 13 pairs of metacentric/submetacentric autosomes and 7 pairs of telocentric chromosomes. The X was a medium-sized submetacentric and the Y a small submetacentric chromosome. This karyotype was quite different from that previously described for C. lepidus from Peru (2n = 36, NF(a) = 68). However, both karyotypes may be easily interrelated by means of four centric fusions, and the chromosome complement of Punian C. lepidus fitted into a previously proposed chromosomal phylogeny of the genus. In addition, the spermatozoa of specimens corresponded to a morphological pattern previously described for other species of Calomys.