title: [DNA barcoding and species and subspecies classification within genus Carassius].
abstract: The classification of Carassius has not been well established due to its great variability and wide distribution. Usually, Carassius is identified as three species: C. carassius, C. cuvieri and C. auratus, the latter including several subspecies, such as goldfish. Out of these subspecies, C. auratus gibelio have recently been thought of as a valid species of Carassius. In this study we collected the 5'end 651 bp segments of the mitochondrial cytochrome c oxidase I (COI) gene from 128 specimens, including C. carassius, C. cuvieri, C. auratus auratus, C. auratus gibelio and C. auratus langsdorfii. All three species of Carassius (C. carassius, C. cuvieri, C. auratus) were found to be valid, meanwhile genetic differentiation between the Eurasian C. auratus and Japanese C. auratus has reached a high level. However, several haplotypes were shared between C. auratus auratus and C. auratus gibelio. Consequently, C. auratus gibelio should be regarded as a subspecies of C. auratus rather than a valid species. Moreover, because both diploids and triploids exist in C. auratus auratus and C. auratus gibelio, ploidy level should not be used as criteria for the classification of species or subspecies in Carassius.
authors.affiliation: Key Laboratory of Aquatic Freshwater Aquatic Biotechnology and Breeding, Ministry of Agriculture of China, Heilongjiang Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin 150070, China. chenglei1982@126.com
authors.forename: Lei
authors.initials: L
authors.lastname: Cheng
authors.forename: Yu-Mei
authors.initials: YM
authors.lastname: Chang
authors.forename: Cui-Yun
authors.initials: CY
authors.lastname: Lu
authors.forename: Ding-Cheng
authors.initials: DC
authors.lastname: Cao
authors.forename: Xiao-Wen
authors.initials: XW
authors.lastname: Sun
mesh_terms: D000818:Animals; D002681:China; D003530:Cyprinidae / Q000145:classification* / Q000235:genetics; D058893:DNA Barcoding, Taxonomic; D029941:Fish Proteins / Q000235:genetics; D014644:Genetic Variation; D008969:Molecular Sequence Data; D010802:Phylogeny
chemical_list: D029941:Fish Proteins