Crabs are the most widely studied marine crustaceans due to their high economic value, ecological significance, and worldwide range in the subtropics and tropics zones. In this study, we adopted a molecular barcoding approach for rapid identification of blue crab species by sequencing the mitochondrial cytochrome c oxidase subunit I gene (COI), which has previously been used for phylogenetic analysis in wide taxonomic groups, and particularly for Crustaceans. The results indicated the evidence of Callinectes sapidus and Portunus pelagicus in different localities along Tunisian coast. Data were confirmed by BLAST analysis (Basic Local Alignment Tool) and phylogenetic trees. The molecular identification showed the ability of the COI region to differentiate between two similar blue crab species, Portunus segnis and Portunus pelagicus, which were confused by morphological analysis. The adoption of this protocol may be useful in revealing the biogeography of these invasive species across Mediterranean and to support the authentication of crab-meat processed products, according to the normative control.

This study investigated the impact of Lernaeolophus sultanus infestation on the nutritional quality of Pagellus erythrinus. A total of 115 specimens was collected from the Gulf of Tunis, of which 12 individuals were infested, mostly females. Muscle tissues from parasitized and unparasitized fish were analyzed for biochemical composition. Infested fish revealed a significant decrease in lipid and ash contents (1.187 and 1.380%, respectively), compared to unparasitized fish (1.483 and 1.460%, respectively) (p < 0.05). Fatty acid profiles were also affected in the infested fish, with reductions in saturated and polyunsaturated fatty acids, especially DHA and EPA, along with an increase in monounsaturated fatty acids. Although the n-6/n-3 ratio and thrombogenic index were altered, they remained within acceptable nutritional limits. These findings indicate that L. sultanus infestation compromises the nutritional quality of P. erythrinus, underscoring the importance of considering parasitic infection in the quality assessment of seafood.