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Title: Parasite effects on the feeding behaviour and functional response of the invasive amphipod Gammarus pulex (Crustacea; Amphipoda)
Author: Ennis, Marilyn
ISNI:       0000 0004 6062 0017
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2016
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Parasites can structure communities and may impact on resource competitive interactions in novel communities. The amphipod Gammarus pulex is invasive in Ireland and in low land river stretches has displaced the native congener Gammarus duebeni celticus. Parasitism may facilitate invasion success by the more efficient use of resources. The functional response (the relationship between prey density and prey consumption) is a means of predicting the likely impact of an invader. In this thesis parasitism by two different acanthocephalan parasite species (Echinorhynchus truttae and Polymorphus minutus) elevated the functional response of G. pulex with either Baetis rhodani or Asellus aquaticus prey. Analysis of prey body part consumption in Baetis rhodani prey by E. truttae parasitised G. pulex revealed that parasitised predators consumed more prey material, partially consumed more prey but consumption distribution was not related to body part. In turn, partial prey consumption may reduce handling time in parasitised predators and may provide a mechanistic explanation for the elevation of functional response parameters. Unconsumed prey provide an additional food source for consumers that are too small or slow to capture larger prey, with consequences for nutrient cycling within freshwater communities. With regards to physiological parameters, non-starved parasitised and unparasitised G. pulex had similar haemolymph protein levels whereas starvation significantly elevated the haemolymph protein level of parasitised G. pulex compared to unparasitised animals. This finding suggested parasite upregulation of host protein resources to compensate for depletion of host haemolymph protein levels during starvation. Additionally, long term starvation did not affect survival rate in parasitised or unparasitised G. pulex but appeared to impact on parasite length in parasitised hosts.. Parasitised invasive predators such as G. pulex may therefore possess traits that allow more efficient use of resources compared to native congeners, which may facilitate and explain the invasion success of this species.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available