Karyotypes and Evolution of Three species of Chinese Squirrels (Sciuridae Mammalia)

The present paper recorded the karyotypes of bone marrow cells of three species of the squirrels collected from southern China.Among them,the karyotypes of two geographical subspecies of Red-abdomen Squirrel (Callosciurus erythraeus castanecventris and C.e.michianus) were much alike.They were found to possess the diploid chromosome number of 40 (I.e.2n=40),FN=72,including 7 pairs of metacentric chromosomes,8 pairs of submetacentric ones,2 pairs of subtelocentric ones and 2 pairs of telocentric ones.No.18 was a pair of subteloentric chromosomes with satellites on the short arms.X-chromosome was a larger metacentric chromosome,Y-chromosome was a smallest subtelocentric one.The differences of the two karyotypes were just the variation of the arm ratio and of the relative lengths of some chromosomes (No.3.4.5.10.11.X and Y).In pernys Long-nosed Squirrel (Dremomys pernyi flavior),2n=40,FN=70.The 19 pairs of autosomes consisted of 8 pairs of metacentric chromosomes,8 pairs of submetacentric ones and 3 pairs of telocentric ones.No.18 was a pair of telocentric chromosomes absent from satellites,though a little below the centric there was a characteristiric ones;Y-chromosome was a medium submetacentric one.In Forrests Rock Squirrel (Sciurotamias forresti),2n=38,FN=72.The 18 pairs of autosomes consisted of 8 pairs of metacentric chromosomes,9 pairs of submetacentric ones and a pair of subtelocentric one,which (I.e.No.18) satellites on the short arms as Calllosciurus erythraeus.Sex chromosomes of both sexes were metacentric chromosomes,among them,X-chromosomes were larger,but Y-chromosome was the smallest.In the last part of this paper,we compared and analyzed the karyotypes of four genera of squirrels in Callosciurini tribe (Sciuridae,Rodentia) and discussed evolution of their karyotypes.