First report on molecular identification of Anisakis simplex in Oncorhynchus nerka from the fish market, with taxonomical issues within Anisakidae.

Alina E Safonova,Konstantin S Vainutis,Anastasia N Voronova

doi:10.21307/jofnem-2021-023

Abstract

Alive anisakids cause acute gastrointestinal diseases, and dead worms contained in food can provoke sensibilization and allergic reactions in humans. Detected in the purchased minced salmon Oncorhynchus nerka nematodes were identified as Anisakis simplex sensu stricto (Anisakidae). We found that recently published phylogenetic trees (reconstructed using different ribosomal and mitochondrial genetic markers) showed independent clusterization of species recognized in the A. simplex sensu lato species complex. This prompted us to undertake this full-fledged molecular genetics study of anisakids from Kamchatka with phylogenetic reconstructions (NJ/ML) and calculated ranges of interspecific and intergeneric p-distances using ITS1-5.8S-ITS2 sequences. We confirmed that molecular markers based on the ITS region of rDNA were able to recognize ‘pure’ specimens belonging to the cryptic species. We offer new insights into the systematics of anisakids. The genus Anisakis sensu stricto should include Anisakis simplex sensu stricto, Anisakis pegreffii, Anisakis berlandi, Anisakis ziphidarum, and Anisakis nascettii. Presumably, two genera should be restored in the structure of the subfamily Anisakinae: Skrjabinisakis for the species Anisakis paggiae, Anisakis brevispiculata, and Anisakis physeteris; and Peritrachelius for the species Anisakis typica. In addition, we provide the short annotated list of some genera of the family Anisakidae, including their diagnoses.

Highlights

A. physeteris (Baylis, 1923) are the causative agents of human gastrointestinal anisakidosis (Karmanova, 2007)
In current taxonomy there is a complex of species A. simplex sensu lato (Mattiucci et al, 1997; Nascetti et al, 1983, 1986) which is made up of the three sibling species: A. simplex sensu stricto, A. pegreffii, and A. berlandi (Mattiucci et al, 2014)
In our opinion, forming a species complex A. simplex sensu lato can lead to the loss of some critical information about the individual characteristics of the biology of parasites, and opportunities to influence the changes taking place in their ethology, pathogenesis, evolution, and divergence

Summary

Introduction

A. physeteris (Baylis, 1923) are the causative agents of human gastrointestinal anisakidosis (Karmanova, 2007). The scope of this study was to accurately identify species of nematodes found in minced salmon O. nerka using the molecular genetics methods and reconstruct phylogenetic relationships within the family Anisakidae which was originally described by Skrjabin and Karokhin (1945) and Skrjabin and Mozgovoy (1973). In order to establish phylogenetic relation ships among anisakids, the phylogenetic tree was reconstructed based on the sequences of the ITS15.8S-ITS2 region with indicated ranges of genetic p-distances (Fig. 1).

Results

Conclusion