The Anisakis simplex complex off the South Shetland Islands (Antarctica): endemic populations versus introduction through migratory hosts

Abstract

Third-stage larvae (L3) of 2 Anisakis nematode species, A. simplex C and A. pegreffii (both A. simplex sibling species complex), were isolated from migrating myctophids around the South Shetland Islands. Gymnoscopelus nicholsi were parasitized by both nematode species, at a prevalence of 22.7% for A. simplex C and 4.0% for A. pegreffii, while Electrona carlsbergi harbored A. simplex C at a prevalence of 9.1%. The ITS-1, 5.8S, and ITS-2 regions of the nematodes were identical to specimens from Pacific Canada or California (A. simplex C) and the coast of China (A. pegreffii), confirming an extensive range of distribution for both species. The occurrence in migrating myctophids coupled with rare findings from other teleosts leads to the conclusion that both species were introduced from outside the Antarctic.

Anisakid Nematode (Ascaridoidea) Life Cycles and Distribution: Increasing Zoonotic Potential in the Time of Climate Change?

“…Life cycle studies of these nematodes have been limited by difficulties in maintaining them alive in the laboratory, culturing sufficient numbers of parasite-free experimental hosts, and creating effective exposure (e.g. Køie and Fagerholm 1995;Køie 2001;Klimpel et al 2004Klimpel et al , 2008Klimpel et al , 2010Mattiucci and Nascetti 2008). However, empirical studies on the distribution and abundance of anisakid larvae in the intermediate and final hosts have revealed important insights into the life cycle biology of these parasites.…”

“…These studies identified the existence of "sibling species" within the ascaridoids, being morphologically very similar but genetically different, having distinct host preferences, life cycles and geographical distribution (e.g. Mattiucci et al 1997Mattiucci et al , 2005Zhu et al 2002;Nadler et al 2005;Marques et al 2006;D'Amelio et al 2007;Klimpel et al 2007Klimpel et al , 2008Klimpel et al , 2010Mattiucci and Nascetti 2008).…”

“…Most important are the three genera Anisakis (whales), Contracaecum (bird, seals), and Pseudoterranova (seals), that can be distinguished morphologically and according to their final host spectrum (e.g. Klimpel et al 2008Klimpel et al , 2010Mattiucci and Nascetti 2008). Life cycle studies of these nematodes have been limited by difficulties in maintaining them alive in the laboratory, culturing sufficient numbers of parasite-free experimental hosts, and creating effective exposure (e.g.…”

“…These studies revealed the existence of nine species, six belonging to two sibling species complexes, the (1) A. simplex complex with A. simplex (s.s.), A. pegreffii, and A. simplex C, the (2) A. physeteris complex with A. physeteris, A. brevispiculata and A. paggiae, and the three species A. typica, A. ziphidarum und A. nascettii (e.g. Klimpel et al 2008Klimpel et al , 2010Mattiucci and Nascetti 2008;Fig. 11.2).…”

“…The Pseudoterranova decipiens complex consists of six different species (P. decipiens s.s. ¼ P. decipiens B, P. krabbei, P. bulbosa, P. azarasi, P. decipiens E, P. cattani) (Mattiucci et al 2007;Mattiucci and Nascetti 2008). Most recently Klimpel et al (2007Klimpel et al ( , 2008Klimpel et al ( , 2010 and studied the species identity within the genus Anisakis by using the following protocol.…”