De novo assembly of genome and development of polymorphic microsatellite loci in the blue swimming crab (Portunus pelagicus) using RAD approach

The blue swimming crab (Portunus pelagicus) is a valuable marine fishery resource in Indo-West Pacific Ocean. So far, rare genetic resource of this species is available. In this report, the restriction-site associated DNA (RAD) approach was employed to mine the genomic information and identify molecular markers in P. pelagicus. A total of 0.82 Gbp clean data were generated from the genome of individual "X2A". De novo assembly produced 85,796 contigs with an average length of 339 bp. A total of 45,464 putative SNPs and 17,983 microsatellite loci were identified from the genomes of ten individuals. Furthermore, 31 pairs of primers were successfully designed, with 16 of them exhibiting polymorphism in a wild population. For these polymorphic loci, the expected and observed alleles per locus ranged from 1.064 to 7.314 and from 2 to 11, respectively. The expected and observed heterozygosity per locus ranged from 0.0615 to 0.819 and from 0.0626 to 1.000, respectively. Nine loci showed high informative with polymorphism information content (PIC) > 0.5. Five loci significantly deviated from Hardy-Weinberg equilibrium in the samples analyzed. No linkage disequilibrium was found among the 16 polymorphic microsatellite loci. This study provided massive genetic resource and polymorphic molecular markers that should be helpful for studies on conservation genetics, population dynamics and genetic diversity of P. pelagicus and related crab species.