Molecular phylogeny of oysters belonging to the genus Crassostrea through DNA barcoding

Abstract

The mangrove dominated Sundarbans is a biodiversity rich complex ecosystem inhabited by a large variety of marine and estuarine species including the oysters. Aquaculture of the edible oysters is regarded as an alternative livelihood of the human population inhabiting this region. The edible oysters necessitate the genetic variation studies among the different species of same genus. Identification of juveniles and immature stages of marine oysters is very difficult using traditional taxonomic approach. DNA barcoding of two oysters belonging to the genus Crassostrea collected from the Sundarbans was done. The nucleotide sequences were very similar to each other with only one nucleotide substitution. 44 barcode sequences belonging to 9 species of the genus Crassostrea revealed that different species formed distinctive clusters. The mean sequence divergence of the novel sequences of Crassostrea gryphoides and Crassostrea cuttackensis were greater than one where as the mean sequence divergence of the other seven species of Crassostrea was very low. The limited number of barcode sequences would bernovercome through the worldwide barcoding initiative, which would refine the results and overcome the shortcomings of using smaller sample sizes.