Genetic Characterization of Portunid Crabs Scylla serrata and Scylla tranquebarica from the West Coast of India Using Random Amplified Polymorphic DNA Markers

Crabs of the genus Scylla (Decapoda: Portunidae) are commercially important and widely distributed throughout the Indian and Pacific Oceans. These crabs have an extended planktonic larval phase in their life cycle which suggests high dispersal potential and the possibility of extensive gene flow between conspecific populations on a geographic mesoscale (tens to hundreds of kilometers). Hence, genetic differentiation studies were carried out for Scylla serrata and S. tranquebarica along the west coast of India using RAPD markers. Twenty five wild specimens of each species were collected from a mangrove area of Ratnagiri district on the west coast of India. Three primers OPE-1, OPE-3 and OPE-4 produced clear and reproducible profiles and were selected for analyzing 20 individuals, each of S. serrata and S. tranquebarica. Primer OPE-4 gave a maximum percentage of 95.23% of polymorphic bands in S. serrata and OPE-3 showed 91% polymorphic bands in S. tranquebarica. Using primers OPE-1 and OPE-3, the two species were clearly clustered into separate groups. The average genetic similarity at the intraspecific level was calculated as 0.64 and 0.73 in S. serrata and S. tranquebarica, respectively, while the interspecies similarity was 0.56. The average polymorphism over all three primers were 83.33 and 63.88% in S. serrata and S. tranquebarica, respectively. A band of 438 bp produced with OPE-1 is diagnostic between the two species being specific to S. serrata.