Population genetic structure of the shovel-nosed lobster Thenus unimaculatus (Decapoda, Scyllaridae) in Indian waters based on RAPD and mitochondrial gene sequences

Abstract

Thenus unimaculatus is one of the most important commercially exploited lobster species in India. The declining trend in catches as well as collapse of fishery in some localities necessitated assessment of the stock structure to manage this resource sustainably. We ascertained the genetic stock structure of T. unimaculatus along the Indian coast, using molecular markers. RAPD and concatenated dataset of mitochondrial DNA genes (partial sequences of Cytochrome Oxidase I and Cytochrome b) were used to detect population differentiation. RAPD markers showed moderate genetic variability with an overall GST value of 0.0442, which indicated low genetic differentiation among subpopulations. The mtDNA dataset revealed high haplotype diversity coupled with very low nucleotide diversity that suggested recent population expansion after a period of low effective population size. The median-joining haplotype network showed no geographical clustering ofhaplotypes.Thelowlevelsofgeneticdifferentiation with non-significant P values (FST =0.0593) may be due high connectivity among shovel-nosed lobster populations and resultant panmixia. This may be due to the planktonic phyllosoma larval phase that extends for(1 month in wild and their transport and dispersal by monsoon currents of Northern Indian Ocean. The results of this study will aid in better management of this dwindling resource.