From mammals back to birds: Host-switch of the acanthocephalan Corynosoma australe from pinnipeds to the Magellanic penguin Spheniscus magellanicus

Abstract

Trophically-transmitted parasites are regularly exposed to potential new hosts through food web interactions. Successful colonization, or switching, to novel hosts, occur readily when ‘donor’ and ‘target’ hosts are phylogenetically related, whereas switching between distantly related hosts is rare and may result from stochastic factors (i.e. rare favourable mutations). This study investigates a host-switching event between a marine acanthocephalan specific to pinnipeds that is apparently able to reproduce in Magellanic penguins Spheniscus magellanicus from Brazil. Detailed analysis of morphological and morphometrical data from acanthocephalans from penguins indicates that they belong to Corynosoma australe Johnston, 1937. Partial fragments of the 28S rRNA and mitochondrial cox1 genes were amplified from isolates from penguins and two pinniped species (i.e. South American sea lion Otaria flavescens and South American fur seal Arctocephalus australis) to confirm this identification. Infection parameters clearly differ between penguins and the two pinniped species, which were significantly lower in S. magellanicus. The sex ratio of C. australe also differed between penguins and pinnipeds; in S. magellanicus was strongly biased against males, while in pinnipeds it was close to 1:1. Females of C. australe from O. flavescens were smaller than those from S. magellanicus and A. australis. However, fecundity (i.e. the proportion of fully developed eggs) was lower and more variable in females collected from S. magellanicus. At first glance, the occurrence of reproductive individuals of C. australe in Magellanic penguins could be interpreted as an adaptive colonization of a novel avian host through favourable mutations. However, it could also be considered, perhaps more likely, as an example of ecological fitting through the use of a plesimorphic (host) resource, since the ancestors of Corynosoma infected aquatic birds.

Acanthocephalan parasites of the flounder species Paralichthys isosceles, Paralichthys patagonicus and Xystreurys rasile from Brazil

“…The parasitization of paralichthyid fish by species of Corynosoma and Bolbosoma turbinella recorded in the present study indicates that these fish are positioned at an intermediate trophic level of the marine food web where they act as paratenic hosts, as has been reported for other species of this family (FUJITA et al, 2016), while marine mammals and birds are final hosts (HERNÁNDEZ-ORTS et al, 2017).…”

Taxonomic revision of species of Haematoloechus Looss, 1899 (Digenea: Plagiorchioidea), with molecular phylogenetic analysis and the description of three new species from Mexico

“…In spite of the supposedly complex and specialized life cycle of species of Haematoloechus that involves a snail and an insect as intermediate hosts and an amphibian as definitive host, host-switching events are possible and have been documented at least in one occasion . These host-switching events are possible for supposedly "host specific" parasite species due to ecological fitting (Janzen 1985), which in this case, is the capacity of the parasite to track widespread, phylogenetically conserved traits in the host, rather than particular host species (Brooks et al 2006;Agosta et al 2010;Hernández-Orts et al 2017). This would explain the multiple host-switching events to different groups of anurans during the evolution of this group of digeneans.…”

A Visitor of Tropical Waters: First Record of a Clymene Dolphin (Stenella clymene) Off the Patagonian Coast of Argentina, With Comments on Diet and Metazoan Parasites

“…Corynosoma australe is a typical acanthocephalan of pinnipeds that can also mature in marine birds (Hernández-Orts et al, 2017). Immature specimens of C. australe have been reported in four species of odontocetes from Argentina (Hernández-Orts et al, 2019).…”