Comparing cestode infections and their consequences for host fitness in two sexual branchiopods: alien Artemia franciscana and native A. salina from syntopic-populations.

Stella Redón,Andy J Green,Marta I Sánchez,Francisco Amat

doi:10.7717/peerj.1073

Abstract

The American brine shrimp Artemia franciscana is invasive in the Mediterranean region where it has displaced native species (the sexual A. salina, and the clonal A. parthenogenetica) from many salt pond complexes. Artemia populations are parasitized by numerous avian cestodes whose effects have been studied in native species. We present a study from the Ebro Delta salterns (NE Spain), in a salt pond where both A. franciscana and native A. salina populations coexist, providing a unique opportunity to compare the parasite loads of the two sexual species in syntopy. The native species had consistently higher infection parameters, largely because the dominant cestode in A. salina adults and juveniles (Flamingolepis liguloides) was much rarer in A. franciscana. The most abundant cestodes in the alien species were Eurycestus avoceti (in adults) and Flamingolepis flamingo (in juveniles). The abundance of E. avoceti and F. liguloides was higher in the A. franciscana population syntopic with A. salina than in a population sampled at the same time in another pond where the native brine shrimp was absent, possibly because the native shrimp provides a better reservoir for parasite circulation. Infection by cestodes caused red colouration in adult and juvenile A. salina, and also led to castration in a high proportion of adult females. Both these effects were significantly stronger in the native host than in A. franciscana with the same parasite loads. However, for the first time, significant castration effects (for E. avoceti and F. liguloides) and colour change (for six cestode species) were observed in infected A. franciscana. Avian cestodes are likely to help A. franciscana outcompete native species. At the same time, they are likely to reduce the production of A. franciscana cysts in areas where they are harvested commercially.

Highlights

The American brine shrimp Artemia franciscana Kellog, 1906 is a key species for the aquaculture industry and a model organism for laboratory research
These included four species whose adults are parasitic in flamingos (Flamingolepis liguloides, F. flamingo, Gynandrotaenia stammeri and Gynandrotaenia sp.), three in shorebirds (Anomotaenia tringae, A. microphallos and Eurycestus avoceti), one in gulls (Wardium stellorae) and one in shelducks (Fimbriarioides tadornae)
A previous study in syntopic populations in Aigues-Mortes in France showed that A. franciscana had fewer cestodes than native, clonal A. parthenogenetica (Sanchez et al, 2012), this might be related to the advantages of sex in resisting parasites

Summary

Introduction

The American brine shrimp Artemia franciscana Kellog, 1906 is a key species for the aquaculture industry and a model organism for laboratory research (e.g., in toxicology, genetics or physiology). In the Mediterranean, native brine shrimps are parasitized by 12 species of avian tapeworms whose final hosts are flamingos, waders, grebes, ducks or gulls (Georgiev et al, 2005; Georgiev et al, 2007; Vasileva et al, 2009). To elucidate the role of parasites in an invasion it is important to study parasite infections in populations of native and alien host species co-ocurring in the same habitat (syntopic populations), but this is difficult because native Artemia have already disappeared from most sites where A. franciscana is detected. We take advantage of a unique opportunity to compare the parasitism of A. franciscana and A. salina in the only site where these two sexual species are known to coexist: the Ebro Delta salterns in north-east Spain

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