An acanthocephalan parasite mediates intraguild predation between invasive and native freshwater amphipods (Crustacea)

Calum MacNeil*, Nina J. Fielding, J. T A Dick, Mark Briffa, John Prenter, Melanie J. Hatcher, Alison M. Dunn

*Corresponding author for this work

    Research output: Contribution to journalReview articlepeer-review

    38 Citations (Scopus)


    1. The balance of predation between closely related invasive and native species can be an important determinant of the success or failure of biological invasions. In Irish freshwaters, the introduced amphipod Gammarus pulex has replaced the native G. duebeni celticus, possibly through differential mutual intraguild predation (IGP). Theoretically, parasitism could mediate such predation and hence the invasion outcome. However, this idea remains poorly studied. 2. In a field survey, we show that the acanthocephalan parasite Echinorynchus truttae is present in more G. pulex populations than G. d. celticus populations. In addition, within parasitised populations, E. truttae is more prevalent in the invader than in the native. 3. We show for the first time that an acanthocephalan parasite mediates predation between its intermediate macroinvertebrate hosts. In a field experiment, E. truttae parasitism of the invader lowered IGP upon the unparasitised native. In laboratory experiments, parasitism of G. pulex significantly reduced their predatory impact on recently moulted female G. d. celticus. Parasitism also appeared to cause reduction in predatory behaviour, such as attacks per contact on precopula guarded female natives. 4. We conclude that higher parasite prevalence in invaders as compared with natives, by mediation of interspecific interactions, could promote species coexistence, or at least slow species replacements, in this particular biological invasion.

    Original languageEnglish
    Pages (from-to)2085-2093
    Number of pages9
    JournalFreshwater Biology
    Issue number12
    Publication statusPublished - Dec 2003


    • Acanthocephalan
    • Biological invasion
    • Echinorynchus truttae
    • Gammarus
    • Intraguild predation


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