Occurrence of larval ascaridoid nematodes in the Argentinean short-finned squid Illex argentinus from the Southwest Atlantic Ocean (off Falkland Islands)

Paolo Cipriani,Lucilla Giulietti,Marialetizia Palomba,Simonetta Mattiucci,Miguel Bao,Arne Levsen

doi:10.1016/j.ijfoodmicro.2019.02.019

Abstract

The Argentinean short-finned squid (Illex argentinus) is an oceanic, neritic species widely distributed off the east coast of South America, representing the most abundant commercially exploited squid species in these waters. Despite the great commercial importance of Argentinean short-finned squid as a food resource, and as frozen product exported to Europe, the presence of zoonotic anisakid nematodes, especially in the mantle of the squid, is poorly known. The occurrence and site of infection of larval ascaridoid nematodes in 70 I. argentinus caught off the Falkland Islands were investigated. Squids were examined using the UV-Press method. In total, 30 nematodes were detected in the viscera and mantle. According to morphology, 27 were third-stage larvae (L3) belonging to genus Anisakis, while three were L3 assigned to Hysterothylacium. Anisakis pegreffii (n = 27) were identified by sequence analysis of the mtDNA cox2 and the partial EF1 α-1 region of nDNA genes; Hysterothylacium aduncum (N = 3) were identified by sequence analysis of the ITS rDNA region. These findings represent the first molecular identification of A. pegreffii and H. aduncum in I. argentinus. Both prevalence (P = 15.7%) and abundance (A = 0.39) of infection with A. pegreffii were low, and even lower values of infection were recorded for H. aduncum (P = 2.1%, A = 0.04). Only 3 out of 70 (4.3%) squids hosted A. pegreffii larvae in the mantle. Larvae infecting viscera were coiled and mainly attached to outer surface of visceral organs. Mantle-infecting larvae were situated in the posterior half. Thus, these results suggest that – although low - the risk of acquiring anisakiasis from consumption of raw, marinated and/or undercooked short-finned squid products still exists.

Highlights

Based on basic diagnostic morphological characters, 27 out of 30 (90%) larval ascaridoid nematodes were recognized as Anisakis third-stage larvae (L3) showing larval Type I characters, while the other 3 specimens (10%) were identified as L3 belonging to genus Hysterothylacium (Ascaridoidea, Raphidascarididae, Nematoda)
Despite the importance of I. argentinus as a food resource in the SW Atlantic Ocean, and as frozen product exported to various European markets, the presence of zoonotic anisakid nematodes, especially in the flesh of the squid, has only been poorly investigated
A few epidemiological reports on anisakid nematodes in I. argentinus exist (Gonzàlez and Kroeck, 2000; Nigmatullin and Shukhgalter, 1990; Sardella et al, 1990; Santos, 1992; Threlfall, 1970), but none of the studies carried out molecular identification, nor provided details on the specific anatomical infection site of the larvae in the squid host

Summary

Introduction

The Argentinean short-finned squid, Illex argentinus (Castellanos, 1960), is the most abundant commercial squid species in the Southwest (SW) Atlantic Ocean (Arkhipkin et al, 2015) It is an oceanic, neritic and highly migratory ommastrephid species, widely distributed along the Patagonian shelf and slope, occurring from 22°S to 55°S (Haimovici et al, 1998, 2014; Hatanaka, 1988). Neritic and highly migratory ommastrephid species, widely distributed along the Patagonian shelf and slope, occurring from 22°S to 55°S (Haimovici et al, 1998, 2014; Hatanaka, 1988) Largest accumulations of this species were observed on the shelf of the Northwest of the Falkland (Malvinas) Islands and on the shelf edge at 45°–47°S (Haimovici et al, 1998). Argentinian export of I. argentinus consists almost entirely of frozen squid products, mostly directed to European (mainly Spain and Italy) and Japanese markets

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