L’aplicació de marcadors genètics per a la identificació d’espècies piscícoles, revela una possible nova espècie del gènere Euthynnus i la presència per primera vegada d’Auxis thazard prop del Mediterrani

Abstract

The importance of a correct identification of species in the fishing sector requires the application of genetic tools like markers, to differentiate species that are very similar morphologically. The species studied are part of the family Scombridae, and correspond to the genera Auxis and Euthynnus. In this study a mitochondrial marker (mtDNA CR) and three nuclear markers (TMO, Rhodopsin and Calmodulin) were used to distinguish species. DNA was obtained from extractions on muscle tissue. Subsequently, PCR was performed and amplification was tested in electrophoresis on agarose gel. In order to clean the product obtained, the ExoSAP protocol was used, followed by the BigDye protocol prior to sequencing. The resulting sequences were analysed with different bioinformatic tools in order to obtain an alignment and thus be able to represent the results by phylogenetic trees. In relation to the genus Auxis, three specimens from Portugal were analysed, which were identified during fishing as Auxis rochei, but once were obtained results by the markers mtDNA CR, TMO and Rodopsina, it was proved that they corresponded to the species Auxis thazard instead of A. rochei. This result contradicts the known distribution of this genus in which A. rochei is the only one considered to be present in the Mediterranean and adjacent areas. The introduction of A. thazard to the Portugal coasts could be due to the temperature increase in water caused by global warming. In relation to the genus Euthynnus, four localities of the species Euthynnus alletteratus were studied, which is distributed throughout the Atlantic Ocean and the Mediterranean. The results by three of the four markers used, showed a divergence between the localities of Portugal and Tunisia, in respect to those of Senegal and Ivory Coast. This result means that a new species of the genus Euthynnus was found because more than two unlinked markers show the same result. The three markers that were functional for this species are: the mitochondrial marker, and the nuclear markers Rhodopsin and Calmodulin