The Mitochondrial Genome Of The Mitten Crab, Eriocheir Japonica Sinensis (Crustacea: Decapoda: Brachyura)and Genetic Marker From Mitochondrial 16S RDNA

The 12940 bp nucleotide sequence of the mitochondrial genome of a brachyura dacapod, Eriocheir japonica sinesis, was determined. The arrangement of 27 genes of the mitochondrial DNA differs from that of the mitochondrial DNA in all other arthropods studied. Rearrangements have been occurred in at least twelve mitochondrial genes, which have drastically altered the gene order of the mitten crab E. japonica sinensis to the putative ancestral pancrustacean (crustacean/insecta) gene order. A four-gene block, a rwo-tRNA gene cluster and six single tRNA genes involved in the rearrangement, the second gene rearrangement type of mitochondrial DNA reported for any pancrustacea arthropod. Comparisons of mitochondrial gene arrangements of decapod suggested that rearrangement of the four gene-block found in Eriocheir is informative for high level phylogenetic study of decapod.To help resolve phylogenetic relationships among the crabs of the genus Eriocheir and the genus Helice (Varunidae), portions of the mitochondrial genome corresponding to the 16S rRNA gene were sequenced for Helice (helice) tientsinesis distributed in China and all species of Eriocheir distributed in China and Japan. The phylogeny analysis supports to transfer the genus Helice from the Sesarmidae to the Varunidae. And supports to the establishment of a separate genus Neoeriocheir, but does not provide justification for the recognition of Platyeriocheir. The results provided more evidence of the conspecific status of three taxa: E. japonica, E. sinensis and E. hepuensis. The mitten crabs distributed in China and Okinawa of Japan constitute a monophyletic group sister to E. japonica from Osaka of Japan suggested that two subspecies of E. japonica: E. j. japonica and E. j. sinensis might be recognized.The mitten crabs and freshwater crabs are different lineages of nonmarine crabs. The former belongs to adults-limnic, the latter to entirely inland forms. The phylogenetic analysis of these twononmarine crabs together with intertidal, supratidal and swimming crabs based on portions of mitochondrial 16S rDNA sequences suggested that Grapsioidea, Ocypodoidea, Potamoidea and Portunoidea arose from a common marine ancestor, and the estimated divergence time are similar. The freshwater crab phylogeny suggested that the genus Sinopotamon and the genus Potamonautes arose from a common ancestor and the estimated divergence time is about 36-44 Mya. The phylogenetic relationship of the mitten crab and other grapsoid crabs suggested that Eriocheir is monophyletic, and the estimated divergence time of the mitten crabs with its marine varunid ancestor is about 8.9~10.9 Mya. This divergent event is correspond with the variance of palegeography in Taiwan islands and Japanese islands during middle Miocene. The dispersal of E. j. sinensis to mainland of China occurred during late Tertiary to early Quaterary estimated according genetic divergence.The fixed substitution of three to four nucleotides between E. j. sinensis and E. j. hepuensis has been found in the sequences of the portions of 16S rDNA and PCR/RFLP studies of 110 samples, from six river valleys in eastern mainland of China. These subspecies-specific restriction sites allow rapid discrimination with the endonuclease Dra I, and therefore can be used as a diagnostic genetic marker for identification of the two subspecies. In addition, a fixed substitution can be used as a diagnostic marker for identification of two haplotypes ofE.j. sinensis.