Search

Triplodon corrugatus is a freshwater bivalve (Hyriidae) endemic to the Amazon, Orinoco and Tocantins basins, and the Piria river. Our understanding of hyriid diversity at, and below, the species level, remains poor. The genetic diversity of T. corrugatus from the Tapajos, Amazon, Tocantins, Irituia and Piria rivers in the north-eastern Brazilian Amazon was investigated. Except for the Irituia, where a single COII–COI haplotype had been fixed, all the other populations had medium to high haplotype diversities, and all populations had low nucleotide diversities. Pairwise fixation indices indicated that all populations were structured, except for comparisons between the Tapajos and Amazon, and the Amazon and Tocantins rivers, which may be explained by a stepping-stone model of migration. AMOVA detected that 81.28% of the variation was among populations. However, STRUCTURE analyses corroborated only the Piria river specimens as comprising a distinct population, which is being maintained by allopatry due to the current isolation between the Piria, and the Amazon and Tocantins basins.

In an effort to develop molecular tools for oyster identification, this study reveals the usefulness of a multiplex polymerase chain reaction (PCR) for the reliable, rapid and low-cost identification of the four oyster species found along the Brazilian coast: Crassostrea gasar, Crassostrea rhizophorae, Crassostrea gigas and Crassostrea sp. Canela originally found at Para, Brazil. In order to perform a simultaneous identification of these species, we used a set of five primers developed and adapted from the cytochrome oxidase subunit I (COI) and internal transcribed spacer 1 (ITS1) fragments, respectively. Amplification was successful in all four species and PCR products were visualized in agarose gel. A single reaction was capable of distinguishing between the species: C. gigas, with two fragments (236 bp for COI and 718 bp for ITS1); C. gasar, with one fragment (718 bp for ITS1); Crassostrea sp., with one fragment (621 bp for ITS1) and C. rhizophorae with two fragments (377 bp for COI and 718 bp for ITS1). This molecular approach provides a simple and rapid identification of the oyster species from the Brazilian coast, thus increasing the efficient and quality of oyster culture programs by reducing the risk of wrong species identification.

A set of ten polymorphic microsatellite loci were isolated and characterized from a CT/GT enriched genomic library of the Brazilian native oyster Crassostrea gasar (Adanson, 1757). These markers were polymorphic and successfully amplified in 21 individuals from Sao Joao de Pirabas, Para state, Brazil. The number of alleles per polymorphic locus varied from 6 to 18 and values of observed and expected heterozygosity ranged from 0.3333 to 1.0000 and from 0.6655 to 0.9361, respectively. Only one of the ten microsatellite loci exhibited deviation from Hardy–Weinberg equilibrium and no evidence of linkage was detected between loci. These informative genetic markers will be very useful in population genetic studies of the mangrove oyster C. gasar. The ten markers also showed cross-species transferability with the native oyster Crassostrea rhizophorae.