Vol. 3, Issue 1 (2018)
Molecular identification and validation of Indian mud crab genus Scylla (Decapoda: Portunidae) based on mitochondrial genes
Author(s): Gatreddi Srinu, G Lakshmana Rao, SK Chand Basha, B Pandayya
Abstract: Effective stock assessment and fisheries management require clearness in their taxonomy for any species. Indian mud crab (genus Scylla de Hann, 1883) is well known for its morphological plasticity and absence species specific taxonomic diagnostic characters due to which became much contentious in their identification. Although this fascinating genus Scylla studied using different morphological and molecular approaches, still there were ambiguities the identification of mud crab species in India. The present study was carried out to find out genetic divergence and to validate phylogenetic position of four species of the genus Scylla (S. serrata, S. olivacea, S. tranquebarica, S. paramamosian) by analyzing 127 partial sequences belongs to four mitochondrial (mt) genes i.e. Cytochrome Oxidase I (COI), Cytochrome b (Cyt b) complex, 12s rRNA and 16s rRNA genes. In the results, the mean intraspecific Kimura 2-parameter distances were consistently higher in all four species for COI gene followed by 12s rRNA and 16s rRNA genes whereas the least distances were observed in Cytochrome b gene. No overlap was found between intraspecific and interspecific distances, suggesting that the existence of distinct barcoding gap to delineate the species boundaries. The Neighbour Joining (N-J) phylogenetic tree for Cytb and 12s rRNA genes formed distinct clusters each containing same species. It can be concluded as Cytb and 12s rRNA sequences could used to delineate evolutionary relatedness with closely related species and this is an effective combinational approach for genetic studies and molecular taxonomic studies on genus Scylla.