Abstract
BackgroundCarassius auratus is a primary freshwater fish with bisexual diploid and unisexual gynogenetic triploid lineages. It is distributed widely in Eurasia and is especially common in East Asia. Although several genetic studies have been conducted on C. auratus, they have not provided clear phylogenetic and evolutionary descriptions of this fish, probably due to selection bias in sampling sites and the DNA regions analysed. As the first step in clarifying the evolutionary entity of the world's Carassius fishes, we attempted to clarify the phylogeny of C. auratus populations distributed in East Asia.ResultsWe conducted a detailed analysis of a large dataset of mitochondrial gene sequences [CR, 323 bp, 672 sequences (528 sequenced + 144 downloaded); CR + ND4 + ND5 + cyt b, 4669 bp in total, 53 sequences] obtained from C. auratus in East Asia. Our phylogeographic analysis revealed two superlineages, one distributed mainly among the Japanese main islands and the other in various regions in and around the Eurasian continent, including the Ryukyus and Taiwan. The two superlineages include seven lineages with high regional specificity that are composed of endemic populations indigenous to each region. The divergence time of the seven lineages was estimated to be 0.2 million years ago (Mya) by a fossil-based method and 1.0-1.9 Mya by the molecular clock method. The antiquity and endemism of these lineages suggest that they are native to their respective regions, although some seem to have been affected by the artificial introduction of C. auratus belonging to other lineages. Triploids of C. auratus did not form a monophyletic lineage but were clustered mostly with sympatric diploids.ConclusionsThe results of the present study revealed the existence of two superlineages of C. auratus in East Asia that include seven lineages endemic to each of the seven regions examined. The lack of substantial genetic separation between triploids and diploids indicates that triploids are not composed of a single independent lineage. The ancient origins and evolutionary uniqueness of the seven lineages warrant their conservation. An overall phylogenetic framework obtained from the present study will be of use for estimating the phylogenetic relationships of Carassius fishes on the Eurasian continent.
Highlights
Carassius auratus is a primary freshwater fish with bisexual diploid and unisexual gynogenetic triploid lineages
In addition to the 35 haplotypes, 29 sequences previously obtained in our laboratory [6], six sequences of C. auratus collected from China [2,28], and one goldfish sequence [2] were added, providing a total of 71 control region (CR) haplotypes for phylogenetic analyses
Phylogenetic analyses based on large data sets of mitochondrial gene sequences (4669 bp) obtained from the East Asian Carassius auratus-complex revealed the existence of two superlineages, one distributed mainly in the Japanese main islands and the other in various regions in and around the Eurasian continent
Summary
Carassius auratus is a primary freshwater fish with bisexual diploid and unisexual gynogenetic triploid lineages It is distributed widely in Eurasia and is especially common in East Asia. Fish of the genus Carassius (Cypriniformes, Cyprinidae), including goldfish, crucian carp, and Japanese crucian carp, primarily inhabit freshwater and are distributed widely in and around the Eurasian continent, including Taiwan and the Japanese islands [1]. Their classification has not been well established due to their great variability, they can be classified into at least three species: C. auratus, C. carassius, and C. cuvieri. To resolve the complicated situations in the natural history and systematics of the fish, one must clarify the biological entities of C. auratus, taking into account the existence of triploids
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
