Biology Ph.D. Dissertations

Parasites alter organismal behavior and interactions in aquatic ecosystems

Date of Award


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Biological Sciences

First Advisor

Paul Moore (Advisor)

Second Advisor

Steven Cady (Other)

Third Advisor

Curtis Blankespoor (Committee Member)

Fourth Advisor

Robert Huber (Committee Member)

Fifth Advisor

Daniel Pavuk (Committee Member)


Though parasites are a ubiquitous in both terrestrial and aquatic ecosystems, the important role parasites play in community ecology is often overlooked. Thus, the goal of my dissertation was to determine how parasites impact ecological communities by altering the personality, foraging behavior, and community interactions of a host. Crayfish Faxonius rustucis are the second intermediate host of the digenetic trematode Microphallus spp. Microphallid load impacted crayfish personality along a bold shy spectrum, causing crayfish to become bolder in the presence of a threatening odor and less exploratory in novel environments, whether or not a food source was present. Additionally, crayfish infected with Microphallus spp. consumed significantly less macrophyte tissue that as parasite load increase. This decrease in consumption was species-specific, with parasite load causing the sharpest decrease in the consumption of Chara sp., followed by Elodea canadensis, Ceratophyllum demersum, and Potamotgeton richardsonii. Additionally, females were more effected by parasite load than males, resulting in a sharper decrease in foraging for the female crayfish. Crayfish were placed in larger community mesocosms with both macrophytes (Chara sp., Myriophallum exalbescens, C. demersum, and P. richardsonii) and animal prey (Campeloma decisum, Dreissena polymorpha, and Dicosmoecus sp.) to determine how microphallid load affected consumption of both plant and animal prey as well as community interactions between the competing animal prey. Macrophyte consumption significantly decreased with increasing parasite load, but the number of animal prey consumed was not affected by parasite load. However, animal weight change was slightly impacted by parasite load, such that D. polymorpha weight remained constant, Dicosmoecus sp. gained about 5% of their body weight, and C. decisum lost approximately 5% of their body weight, which could indicate shifts in the competition between these species. Overall, Microphallus sp. alter crayfish behavior. Because crayfish are keystone species in aquatic habitats, this shifting behavior can have community-level impacts.