The species Onychostoma rara,belonging to Cyprinidae,Cypriniformes,is endemic to China and distributed only in the Yuanjiang River and the Xijiang River systems.The species has been listed as the endangered one now.To evaluate the present state of genetic diversity of Onychostoma rara,the sequence polymorphism of mtDNA D-loop of the species is studied for the first time on the basis of determination of the 478 bp sequences from 3′ end of mtDNA D-loop in the 30 individuals of the species collected from the Q...