1Dalian Fisheries University, Dalian 116023, China, 2Hubei Fisheries Science Research Institute, Wuhan 430071, China, 3Graduate School of Fisheries Sciences, Hokkaido University, Hakodate 041-8611, Japan
Natural triploid and asexually reproducing clonal diploid loaches are found in Japanese populations of the loach, Misgurnus anguillicaudatus. The distribution of polyploid loaches in Chinese populations has not been studied except for a few cytogenetic studies that described the occurrence of polyploidy. In the present study, we examined the ploidy status of a total of 762 specimens collected from 29 localities in China by measurements of erythrocytic cell nucleus after the ploidy determination performed by chromosome counting and DNA content flow-cytometry in selected individuals. Among diploid, triploid and tetraploid individuals, significant differences were detected in major and minor diameters of nucleus, and also nuclear volume. A few triploid (3n) loaches were detected in relatively wide areas including Hohhot, Neimenggu (3.3%), Tianjin (5.3%), Hangzhou, Zhejiang (3.3%), Chibi, Hubei (3.3%), Honghu, Hubei (6.7%) and Shashi, Hubei (3.3%). However, tetraploid (4n) loaches were detected only in Chibi (3.3%), Honghu (16.7%), Shashi (3.3%) and Ezhou (5.0%) from Hubei province. These results indicate that there are several localities in China exhibiting relatively higher frequencies of polyploid loaches.