Karyotype Analysis of the Common Mole Rat (Tachyoryctes Splendens) from Different Localities in Ethiopia

Abstract

In the present study, karyotypes of the east African mole rat, Tachyoryctes splendens, specimens from nine localities in Ethiopia namely; Bure, Chiro, Debre Sina, Entoto, Haramaya, Masha, Mugo, Sebeta and Ziway, were analyzed using conventional chromosome preparation method from the bone marrow cells. 2n=48 chromosomes were counted for all the specimens of all the nine localities. The chromosomes fall into metacentric, submetacentric, subtelocentric and telocentric classes, with the latter being the most frequent type. In all the cases, the X chromosome was the largest in the complement and it was metacentric, except for Entoto and Sebeta specimens, in which case it was submetacentric. The Y chromosome was smaller than the X chromosome and it was also metacentric in all the karyotypes except in Debre Sina where it was submetacentric. In all the karyotypes, small autosomal metacentric chromosomes were present, but their number varied as three, four and five pairs in different karyotypes. Clear submetacentric autosomal chromosomes were observed in the karyotypes of Masha and Mugo specimens only. Autosomal fundamental number ranged from 52 to 66. Generally, karyotypic similarity corresponded with population geographic proximity. In total, six different karyotypic forms were recognized which can be grouped as Masha-Mugo, Bure, Debre Sina, Entoto-Sebeta, Ziway, and Haramaya-Chiro karyotypes. The presence of different numbers of metacentric autosomal chromosomes observed in different karyotypes, unaccompanied by a change in diploid chromosome number, could probably be due to pericentric inversions rather than due to Robertsonian translocations.