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 mostimportant commercially exploited lobster species inIndia. The declining trend in catches as well ascollapse of fishery in some localities necessitatedassessment of the stock structure to manage thisresource sustainably. We ascertained the genetic stockstructure of T. unimaculatus along the Indian coast,using molecular markers. RAPD and concatenateddataset of mitochondrial DNA genes (partialsequences of Cytochrome Oxidase I and Cytochromeb) were used to detect population differentiation.RAPD markers showed moderate genetic variabilitywith an overall GSTvalue of 0.0442, which indicatedlow genetic differentiation among subpopulations.The mtDNA dataset revealed high haplotype diversitycoupled with very low nucleotide diversity thatsuggested recent population expansion after a periodof low effective population size. The median-joininghaplotype network showed no geographical clustering of haplotypes. The low levels of genetic differentiationwith non-significant Pvalues (FST=0.0593) may bedue high connectivity among shovel-nosed lobsterpopulations and resultant panmixia. This may be dueto the planktonic phyllosoma larval phase that extendsfor[1 month] in wild and their transport and dispersalby monsoon currents of Northern Indian Ocean. Theresults of this study will aid in better management ofthis dwindling resource.