Molecular identification of native oysters on the coast of Maranhão, Brazil

Abstract

Oysters are found along the whole coast of Brazil. The phenotypes of the species vary considerably according to the characteristics of the habitat. The present study investigated the existence of different oyster species of the genus Crassostrea on the coast of Maranhão, using the Multiplex PCR technique and DNA Barcoding. The results of the Multiplex PCR revealed two distinct bands characteristic of the species C. gasar and C. rhizophorae in a total of 135 samples analyzed. The sequencing of the COI gene of 98 samples produced a 695 bp fragment and 15 haplotypes for C. gasar and 640 bp and eight haplotypes for C. rhizophorae. The haplotype tree divided the two species clearly into different clades with 100% bootstrap support. Intraspecific genetic divergence was 0.2% in both species, while interspecific divergence was 23.6%. The similarity between the sequences generated and those available in BoldSystems ranged from 97.01% to 98.37% for C. rhizophorae and from 97.55% to 99.84% for both C. gasar and C. brasiliana, reinforcing the taxonomic problems in this group, which supports the synonymization of these species. The DNA barcoding permitted the reliable identification of the samples and confirmed the existence of two species of oyster in the study area.