Defense Date


Document Type


Degree Type

Master of Science

Degree Name

Biological Sciences

First Advisor

Christopher Blanar, Ph.D.

Second Advisor

Lauren Nadler, Ph.D.

Third Advisor

Jeffrey Hoch Ph.D.


Complex life cycle, experimental infection, metacercariae, trematode, behavioral manipulation, Gulf killifish


Trophically transmitted parasites may manipulate their hosts’ phenotype (e.g., behavior, physiology, morphology) to increase the likelihood of transmission to the definitive host. In fishes, stable social groups develop familiarity over time through repeated interactions among individuals, and social preferences are often developed due to familiarity. Consequently, fishes often shoal with familiar fishes, a behavior that is likely to be protective against predation. Parasites may alter fish social dynamics in two ways: by decreasing association with familiar individuals, thereby isolating infected fish and making them more susceptible to predation by definitive hosts; and/or by incentivizing uninfected individuals to avoid infected fish in their shoal. In the present study, I tested whether Gulf killifish Fundulus grandis experimentally infected with Euhaplorchis sp. exhibited altered social preferences based on familiarity. I used a choice test methodology, allowing focal fishes to choose to associate with familiar or unfamiliar conspecific fishes held in transparent enclosures. I found that focal fish infection status had no impact on how far the fish swam. Familiarity of the stimulus groups also had no impact on who the focal fish spent more time with. Infection status and familiarity of the stimulus groups had no impact on who the focal fish spent more time with as well. Focal fish did not show a preference for familiarity or infection. Although Euhaplorchis sp is known to increase the probability of predation of its hosts by birds, my results suggest that it does not do so by altering host shoaling behavior.