Dissertation Research: Reciprocal interactions between host behaviors, steroid hormones, and parasites

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In human and non-human animals, behavior influences the risk of encountering and becoming infected by parasites. For example, the types of food one eats, places one travels, and risky behaviors one engages in are all important in determining parasite risk. Another important, but less well studied, aspect of the interaction between behavior and parasitism explores how parasites change host behavior after infection. Parasites of people (for example, Toxoplasma gondii) and non-human animals can change the behavior of their hosts, and appear to do so by changing the host's brain chemistry or hormone levels. For example, two trematode parasites infecting California killifish increase the frequency of risky behaviors in the fish, and one of these parasites is associated with changes in the fish's brain chemistry. This study will explore how killifish behavior and hormone levels influence encounter and infection rates with parasites, and how infection changes the fish's behavior and hormone levels. Laboratory behavioral experiments, field experiments in the killifish's natural habitat, and molecular techniques will be used to explore these questions. The researchers predict that less social, more active killifish encounter parasites more often, and that infection changes host levels of androgens, estrogens, and glucocorticoids (types of hormones) and makes the fish more bold, asocial, and active. This project is important because parasites are commonly overlooked in behavioral studies, yet are likely to have very important implications for host behavior and physiology across the animal kingdom. Additionally, the PhD student running this project has a strong history of outreach. She will involve undergraduate and high school students in this project, and this grant will allow her to teach the students molecular techniques for measuring hormone levels, in addition to ecological and behavioral techniques.