Molecular identification of Anisakis and Hysterothylacium larvae incommercial cephalopods from the Spanish Mediterranean coast

Abstract

This study aims to investigate the occurrence of nematode larvae in commercial cephalopods in theWestern Mediterranean Sea. A total of 202 animals comprising 123 broadtail shortfin squid (Illex coinde-tii), 34 European squid (Loligo vulgaris) and 45 common octopus (Octopus vulgaris) were examined usingenzymatic digestion. A total of 31 larvae were isolated (prevalence: 14.6%) and identified using molecularanalyses which included PCR and sequencing of the ITS (ITS1-5.8S rDNA-ITS2) region. Phylogenetic treeinferred from ITS sequences yielded supported relationships for Anisakis (P: 12.2%) and Hysterothylaciumspecies (P: 4.1%). All parasites were found parasitizing I. coindetii and, as expected, A. pegreffii presentedthe highest prevalence (11.4%). A. physeteris was also found with a lower prevalence (1.6%) but confirmingthe role of the broadtail shortfin squid as paratenic host and, its potential host for anisakidosis transmis-sion. A hybrid larva between Anisakis simplex and A. pegreffi was also identified. All Anisakis larvae werefound within the visceral cavity; in contrast most of the Hysterothylacium larvae were isolated from themantle. A significant correlation was found between total nematode prevalence and depth, explained bythe presence of larger broadtail shortfin squids inhabiting deeper depths. Therefore, the results obtainedin the present study improve the knowledge of the occurrence of Anisakis and Hysterothylacium species inthe I. coindetii from the Spanish Mediterranean Sea highlighting the importance of considering I. coindetiias a potential hazard for humans if it is consumed raw or not well cooked and the need of further researchin other cephalopods.