Karyotype Characteristics of Onychostoma rara from South China

The karyotype of Onychostoma rara, which is endemic to China, was investigated for the first time using the methods of culture of kidney cell in vivo, and the numbers, sizes and morphology of the chromosomes in the species were reported. A total of 210 mitotic metaphases from 10 individual fish of O. rara, which were collected from the Pan yang River (located in the Pearl River system, China), showed that the modal number of chromosomes (82.38%) was 2n=50. The chromosome formula of the species could be stated as 2n=50=12M+16SM+10ST+12T and the arm number was NF=78. The average size of the chromosomes in the species varied from 8.592 to 13.872 μm, and its total length of haploid chromosomes was 302.777±23.331μm. No heteromorphic sex chromosome was distinguished in these species. This study provides new and fundamental knowledge on karyotypes in O. rara which may advance evolutionary understanding, enhance conservation practices and the chromosomal manipulations used in aquaculture in these species.