New Insights on the Diversity, Ecology and Genetic Population Structure of Anisakis spp. from Fish and Cetacean Hosts from Northeast Atlantic Waters

In the last 25 years, nematode parasites of the genus <i>Anisakis</i> have attracted international attention from various socio-economic sectors, with serious concern about the impact of these parasites on seafood quality and safety, and public health (related to both zoonoses and allergy). A knowledge-based understanding of the population structure of <i>Anisakis</i> spp. is useful to provide valuable data about the infection dynamics, host specificity and its ability to adapt to local environments and to climate change by adapting to the food-web structure. This study first aimed to investigate the taxonomic biodiversity of <i>Anisakis</i> spp. collected from commercial fish and cetacean species from the most significant Northeast Atlantic fishing grounds and evaluate the ecological connections of <i>A. simplex</i> and <i>A. pegreffii</i> (L3 and adults) in cetaceans and fish from NW Spain, through the analysis of their genetic diversity and population structure. A total of 1399 <i>Anisakis</i> spp. L3 larvae from six fish species and 475 adults from six cetacean species were identified using the ITS rDNA region as a molecular marker. Molecular identification allowed for the first detection of <i>A. berlandi</i> in European waters parasitizing the long-finned pilot whales <i>Globicephala melas</i> and the first report of <i>A. nascettii</i> and <i>A. zhiphidarum</i> infecting the striped dolphin <i>Stenella coeruleoalba,</i> as well as the identification of <i>A. simplex, A. pegreffii</i> and the hybrid genotype between both species. The analysis of the mitochondrial cytochrome oxidase 2 gene of <i>A. simplex</i> and <i>A. pegreffii</i>, the most prevalent species in FAO area 27, revealed panmictic populations for both species with high haplotype diversity. The predatory-prey relationship involving two major fish species (European hake and blue whiting) and the common dolphin appears to provide an important mechanism for maintaining genetic diversity and structure in major <i>Anisakis</i> species in the NE Atlantic.