Mitochondrial DNA variation reveals distinct lineages in Penaeus semisulcatus (Decapoda, Penaeidae) from the Indo-West Pacific Ocean

Penaeus semisulcatus, the green tiger prawn, is an ecologically and economically important penaeid shrimp in the Indo-West Pacific region, especially in rice-shrimp farming and capture fisheries in Bangladesh and Sri Lanka, respectively. Genetic variation and phylogeography of samples of this species from Bangladesh and Sri Lanka were studied utilizing different mitochondrial DNA markers, i.e. cytochrome oxidase subunit 1 (CO1), control region (CR) and 16S rRNA genes. No evidence of population structure was observed in Bangladesh, but distinct variations were found among the Sri Lankan samples (phi(ST) = 0.04, p=.002; F-ST = 0.07, p=.001), with the western sample differing from the northwestern and southern samples. The Bangladesh population had lower genetic diversity than two of the three Sri Lanka populations. The phylogeography of P.semisulcatus revealed two distinct mitochondrial DNA (mtDNA) lineages, one in the Western Pacific Ocean and second in the Indian Ocean. The Bangladesh samples showed highest levels of similarity with samples from Sri Lanka, India and Malaysia, with the Bangladesh and Sri Lanka populations sharing the most common recent ancestry. Among the Indian Ocean samples, high levels of variation were observed in the samples from Iran, indicating admixture of two distinct mtDNA lineages, one shared by the populations from the Bay of Bengal and the other possibly originating from Eastern Africa. The genetic and phylogeographic information obtained in this study will be useful in appropriate planning for management and conservation of shrimp fisheries in Bangladesh and Sri Lanka, and in the Indo-West Pacific region.