A barcode for the authentication of the snappers (Lutjanidae) of the western Atlantic: rDNA 5S or mitochondrial COI?

The increasing demand for fishery resources in recent years has stimulated a growth in the output of processed products, which has made the fraudulent substitution of species a common practice. In the present study two different protocols were evaluated for the molecular authentication of lutjanid species, one based on the banding pattern of the nuclear rDNA 5S gene, and the other on the sequences of the mitochondrial Cytochrome Oxidase subunit I (COI) gene. A total of 132 samples were analyzed from specimens identified previously as belonging to seven lutjanid species (Lutjanus purpureus, Lutjanus synagris, Lutjanus vivanus, Lutjanus jocu, Lutjanus analis, Ocyurus chrysurus, and Rhomboplites aurorubens), as well as unidentified individuals. The results indicate the absence of a species-specific rDNA 5S banding pattern in lutjanids. However, the 1131 bp fragment of the COI gene not only discriminated the identified lutjanid species systematically, but also defined the species of the unidentified specimens, identifying another two species from the database, Lutjanusbucanella and Lutjanuscyanopterus. The species were represented by well-defined consensual clades in the phylogenetic trees, supported by the interspecific distances and the mutations characteristic of each species. This segment of the COI gene proved to be a robust tool for the molecular authentication of lutjanid species.