DNA barcode of tilapia fish fillet from the Brazilian market and a standardized COI haplotyping for molecular identification of Oreochromis spp. (Actinopterygii, Cichlidae)

Abstract

The globalized production chains of fish products have been posing increasing difficulties in carrying out proper food control on any level. In case of species identification, morphological examinations that are usually efficient to identify entire fishes, fresh or frozen, fail when applied to fish derivative products, such as fillets or canned meat. In this study we evaluated the global distribution of tilapia COI haplotypes and haplogroups, contrasting diversity in native range and areas where Oreochromis spp. are regarded as introduced. Introduced areas showed a lower diversity of haplotypes comparatively to native areas, evidencing that cultures in different parts of the world originated from a few strains in Africa. Afterwards, evaluating COI diversity from tilapia fillets of the Brazilian market, we concluded that diversity in Brazilian cultures is similar to other countries where they were introduced, but it was highly heterogeneous among brands. Since part of the global movement on tilapia culture relies on crossbreeding of tilapia lineages, the difficulty in defining specific strains of tilapia through DNA barcodes is thought to increase. Our haplotyping system presents a practical form of molecular identification for tilapia products that may be useful in future taxonomic reviews. However, the estimated genetic diversity of Oreochromis through the COI marker does not necessarily reflect the diversity of species in the group, but rather the evolutionary history of this marker. Nevertheless, given the costs and feasibility of analyzing multiple markers, such as microsatellites, the current haplotyping standard is an improvement over the previous system.