Morphometry and molecular diagnosis of Anisakis (Nematoda: Ascaridida) in Merluccius gayi (Chordata: Gadiformes) and Dosidicus gigas (Mollusca: Teuthida) in Biobío Region, Chile

Abstract

Species of the genus Anisakis (Nematoda: Anisakidae) are indirect life-cycle marine parasites. Planktonic crustaceans serve as first intermediate hosts, while fish and cephalopods as second intermediate or paratenic hosts, and finally the cycle is completed in cetaceans, marine mammals that are the main definitive hosts of the genus. In the life cycle, Anisakis larvae can be ingested by humans as accidental hosts, which can cause anisakiasis, a zoonosis acquired through the consumption of raw or marinated fish and cephalopods. These nematodes have a cosmopolitan distribution; however, their diversity has been poorly studied in the southern hemisphere. Therefore, diversity of Anisakis spp. larvae present in two host species in Chile was evaluated by combining morphometric and genetic analysis. For this purpose, Anisakis spp. larvae were collected from the abdominal cavity of hake Merluccius gayi and the Humboldt squid Dosidicus gigas from fishing ports in the Biobío Region, Chile. Morphometric characterization of Anisakis spp. larvae consisted of measuring the length of the esophagus, esophageal ventricle, tail, total length and maximum body width. The nuclear ITS (ITS1-ITS2) and mitochondrial COX2 molecular regions were used for genetic analysis. Morphometric results revealed that Anisakis larvae extracted from D. gigas were significantly longer than those collected from M. gayi, suggesting high host-dependent phenotypic variability. Molecular and phylogenetic analyses determined the presence of Anisakis pegreffii in both host, however, demonstrated low genetic differentiation and nucleotide diversity among sequences, indicating low genetic variability for the data set. This work constitutes the first molecular record of A. pegreffii in intermediate / paratenic hosts from the coast of Chile.