[A cytogenetic study of four species of turtle from China]

The karyotypes, C-banding and Ag-NORs of four species of turtle from China have been studied. The results demonstrated that Cuora aurocapitata has 2n = 52(14M + 2SM + 4ST + 6T / 26m), NF = 72, 8 + 5 + 13(karyotypic formulae). Its secondary constrictions (SC) located on No. 1 p inter of group I; C. trifasciata has 2n = 52(12M + 4SM + 4ST + 6T + 26m), NF = 72, 8 + 5 + 13; Cistoclemmys flavomarginatus has 2n = 52(16M + 4ST + 6T + 26m), NF = 72, 8 + 5 + 13. The SC is also on No. 1 p inter of group I; C. galbinifrons has 2n = 52(16M + 2SM + 4ST + 6T + 24m), NF = 74, 9 + 5 + 12. Four pairs of SC of C. galbinifrons are on No. 1 p inter, No. 3,7 p par and No. 6(X chromosome) q per of group I. The heteromorphic chromosomes related with sexuelity were discovered in C. galbinifrons, while there is no that in other three species. All the centrometric regions of the chromosomes for the four studied species showed the various degree staining of C-positive. Only one homologous pair of Ag-NOR, is found for C. galbinifrons, which locate on No. 5 q per of group II. The Ag-NOR, of other three species lies in No. 7 q ter of group I. The mechanism of the karyotypic evolution is discussed. Individual evolutional mechanism of an heteromorphic sex pair of chromosomes.