Parasite-modified behaviour in freshwater systems: Context dependence and the ecological role of signaling molecules

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Long term goal: Advance our knowledge of the ecological significance of parasite-modified behaviour in aquatic communities. Many parasites can modify their host's behaviour, but the impacts on parasite transmission and other members of aquatic communities are often unclear. Most examples of parasite-mediated behaviour focus on host-parasite interactions that involve trophic transmission. However, parasite transmission is often non-trophic, involving transmission of parasite stages that are short-lived with limited dispersal capabilities. Similar to trophically-transmitted stages, it could be advantageous to modify host behaviour to increase their likelihood of encountering the next host in the life cycle. However, the role of altered behaviour in non-trophic parasite transmission, as well as the mechanisms underlying these changes are mostly unknown. Short-term objectives: 7 HQP will be trained to integrate taxonomic, behavioural, and biochemical data from field and lab experiments to explore the role of chemical communication in parasite-mediated host behaviour by trematode parasites. I focus on freshwater trematodes because they can cause significant disease in humans, livestock, and wildlife. Further, trematodes are ubiquitous in wetlands, many species must infect snails at one point in their life cycle, and many of the latter transmit from snail-snail (e.g. echinostome trematodes). My research program will make several important contributions to understanding factors that affect species interactions. Determining behavioural responses among snails and parasites (Objective 1), and plants (Objective 2) in a controlled lab setting will establish the contexts for species interactions in aquatic communities. Further, these results will disentangle the influence of parasites and infected hosts on behavioural interactions in ecological communities. Using an integrative approach to properly identify snail hosts, trematode parasites, and plants will resolve taxonomic disagreements that impede our ability to understand species interactions. Further, accurate identification is essential to fundamental aspects of trematode biology (e.g. inferences about host specificity and life cycles), parasite epidemiology (e.g. inferences about transmission), and mollusc conservation in freshwater systems (e.g. assessments of gastropod biodiversity and ecosystem health). To explore the mechanistic role of chemical communication in species interactions, I will characterize oxylipins (oxidized fatty acid signaling molecules) from snails, parasites, and plants (Objective 3). These data will suggest which oxylipins influence species interactions. I will determine whether some of these specific molecules or cocktails of molecules explain behavioural patterns (Objective 4). Understanding the role of chemical communication benefits parasite community ecology and epidemiology by improving our knowledge of mechanisms that mediate host-parasite interactions.