author(s)
S Umamaheswari, P Saravana Bhavan, R Udayasuriyan, C Vadivalagan and R Kalpana

abstract
This study dealt with DNA barcoding of five species of Brachyuran crabs, of which four marine species (Portunus sanguinolentus, Charybdis natator, Portunus pelagicus and Portunus trituberculatus, and one freshwater species, Travancoriana napaea, served as an out group. The amplified DNA sequences against the universal primers, LCO1490 and HCO2198 for mt-COI gene revealed ~700 bp in each species, and they showed 89-98% similarity. The phylogenetic information revealed that nucleotide substitutions occurred at different levels than that of nucleotide saturation. All the subjected marine crab species were aligned in one cluster along with retrieved species. And some other retrieved marine crab species were aligned in two separate clusters. T. napaea was alone aligned in an independent cluster at the base of the phylogenetic tree. Therefore, these sequences are conserved and less subjected to evolutionary forces and thus these species are genetically distinct, but closely related. Hence, all the subjected crab species have originated from a common ancestor. T. napaea was also subjected to phylogenetic divergence with six retrieved freshwater crab species and showed 89% similarity. The phylogenetic information revealed that the retrieved freshwater crab species were aligned in one cluster, and the subjected T. napaea was alone sat in a separate cluster as in the previous case. Hence, all the freshwater crab species have originated from a very close and common ancestor.