DISSERTATION RESEARCH: How life history influences host manipulation by parasites in the California fiddler crab, Uca crenulata

University Of California-Riverside, Riverside CA

Investigators

Abstract

Many parasites manipulate host behavior to enhance parasite transmission and reproductive success. Often ?risky? behaviors become intensified and make intermediate hosts more susceptible to predation by final hosts; this step is crucial for life cycle completion. While parasitism is the most common lifestyle on Earth, many aspects of host-parasite relationships remain poorly understood. First, parasites exhibit considerable variation in their manipulative effort. Recent theoretical models suggest that this variation arises from differences in parasite lifespan. Shorter-lived parasites should exhibit more manipulative effort than longer-lived species to achieve transmission before death. Manipulative strategies may also vary across parasite development to minimize mortality. Specifically, parasites should suppress risky host behaviors when immature, and enhance them once infective to final hosts. In addition, little is known about the relationship between manipulative parasites and host sexual signals. While parasites generally decrease a host?s ability to attract mates and reproduce, manipulative species could increase sexual signals to make hosts more attractive to predators, but also to potential mates. Paradoxically, infected individuals would experience higher short-term mating success, as well as increased mortality via predation. This view runs counter to conventional models, and would reveal a new role for parasites in sexual signal evolution. These hypotheses will be tested in the lab and field using naturally and experimentally infected fiddler crab populations from Southern California. Courtship and anti-predator behaviors will be quantified across parasite development to determine how parasitic effects change through time. Predation trials will reveal how parasites influence host predation and mortality. This research will contribute to our understanding of host-parasite evolutionary dynamics and how manipulative parasites influence host sexual signal evolution. Zuk and Mora will disseminate their results to outreach organizations and to the general public during citizen science events organized by Mora and nature reserve managers.