title: Complete mitochondrial genomes of Carcinoscorpius rotundicauda and Tachypleus tridentatus (Xiphosura, Arthropoda) and implications for chelicerate phylogenetic studies.
abstract: Horseshoe crabs (order Xiphosura) are often referred to as an ancient order of marine chelicerates and have been considered as keystone taxa for the understanding of chelicerate evolution. However, the mitochondrial genome of this order is only available from a single species, Limulus polyphemus. In the present study, we analyzed the complete mitochondrial genomes from two Asian horseshoe crabs, Carcinoscorpius rotundicauda and Tachypleus tridentatus to offer novel data for the evolutionary relationship within Xiphosura and their position in the chelicerate phylogeny. The mitochondrial genomes of C. rotundicauda (15,033 bp) and T. tridentatus (15,006 bp) encode 13 protein-coding genes, two ribosomal RNA (rRNA) genes, and 22 transfer RNA (tRNA) genes. Overall sequences and genome structure of two Asian species were highly similar to that of Limulus polyphemus, though clear differences among three were found in the stem-loop structure of the putative control region. In the phylogenetic analysis with complete mitochondrial genomes of 43 chelicerate species, C. rotundicauda and T. tridentatus were recovered as a monophyly, while L. polyphemus solely formed an independent clade. Xiphosuran species were placed at the basal root of the tree, and major other chelicerate taxa were clustered in a single monophyly, clearly confirming that horseshoe crabs composed an ancestral taxon among chelicerates. By contrast, the phylogenetic tree without the information of Asian horseshoe crabs did not support monophyletic clustering of other chelicerates. In conclusion, our analyses may provide more robust and reliable perspective on the study of evolutionary history for chelicerates than earlier analyses with a single Atlantic species.
authors.affiliation: 1. School of Life Sciences, Graduate School, Kyungpook National University, Daegu 702-701, South Korea.
authors.forename: Su Youn
authors.initials: SY
authors.lastname: Baek
authors.affiliation: 2. Department of Biology, Teachers College & Institute for Phylogenomics and Evolution, Kyungpook National University, Daegu 702-701, South Korea.
authors.forename: Eun Hwa
authors.initials: EH
authors.lastname: Choi
authors.affiliation: 2. Department of Biology, Teachers College & Institute for Phylogenomics and Evolution, Kyungpook National University, Daegu 702-701, South Korea.
authors.forename: Kuem Hee
authors.initials: KH
authors.lastname: Jang
authors.affiliation: 2. Department of Biology, Teachers College & Institute for Phylogenomics and Evolution, Kyungpook National University, Daegu 702-701, South Korea.
authors.forename: Shi Hyun
authors.initials: SH
authors.lastname: Ryu
authors.affiliation: 3. Department of Science Education, Graduate School, Kyungpook National University, Daegu 702-701, South Korea.
authors.forename: Sang Myeon
authors.initials: SM
authors.lastname: Park
authors.affiliation: 4. Department of Life Sciences, Yeungnam University, Gyeongsan, Gyeongsangbuk-do 705-717, South Korea.
authors.forename: Ho Young
authors.initials: HY
authors.lastname: Suk
authors.affiliation: 5. Department of Biology, College of Natural Science, Daegu University, Gyeongsan, Gyeongsangbuk-do 712-714, South Korea.
authors.forename: Cheon Young
authors.initials: CY
authors.lastname: Chang
authors.affiliation: 2. Department of Biology, Teachers College & Institute for Phylogenomics and Evolution, Kyungpook National University, Daegu 702-701, South Korea.
authors.forename: Ui Wook
authors.initials: UW
authors.lastname: Hwang
mesh_terms: D000818:Animals; D001483:Base Sequence; D001499:Bayes Theorem; D002874:Chromosome Mapping; D016000:Cluster Analysis; D017931:DNA Primers / Q000235:genetics; D054629:Genome, Mitochondrial / Q000235:genetics*; D006737:Horseshoe Crabs / Q000235:genetics*; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D017931:DNA Primers
keywords: Carcinoscorpius rotundicauda; Horseshoe crabs; Mitochondrial genome; Phylogenetics; Tachypleus tridentatus; Xiphosura