Morphological and genetic identification of Pennella instructa (Copepoda: Pennellidae) on Atlantic swordfish (Xiphias gladius, L. 1758)

During the last years the presence of parasites in commercial fish species has increased becoming an emergent major sanitary problem. For seafood companies the control of this biological hazard is turning into a priority issue, as quality of the products is now being seriously compromised. The swordfish Xiphias gladius, as one of the most important commercial species among European markets, has been inspected for the presence of pennellids. A total of 214 mesoparasitic copepods were sampled for epidemiology and genetic analysis, 5 pennellid cephalothoraxes' for morphological and genetic studies and 50 slices of parasitized swordfishes were examined for internal lesions and diagnostics on the basis of morphological characters. All hosts were captured in Atlantic waters. Pennella instructa was morphologically identified as the only metazoan species in the 5 cephalothoraxes. Morphological characters and internal and external lesions caused by P. instructa were acutely described. Prevalence and mean Intensity of infection were determined for the total fishes parasitized. Copepods were molecularly characterized and the phylogenetic relationships were explored based on 18S and 28S rDNA sequences. Phylogenetic analyses using maximum likelihood models were performed including pennellid external portions and cephalothoraxes (morphologically identified as P. instructa). All pennellid samples were clustered into the same clade with bootstrap values of 100% for both genes sequenced. The prevention of rejections due to these parasites must be the first step to ensure safer and high quality standard products to final consumers. Monitoring actions and proactive self-inspections including preventive and corrective measures should be more intensively integrated into HACCP systems of seafood companies.