Defense Date

8-11-2023

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Christopher Blanar, Ph.D.

Second Advisor

Lauren Nadler, Ph.D.

Third Advisor

David Kerstetter, Ph.D.

Keywords

parasites, Euhaplorchis, trematodes, Fundulus grandis, killifish, fast-starts, escape responses, predation risk, behavioral manipulation, trophic transmission

Abstract

Parasites with complex, multi-host lifecycles often engage in host behavior manipulation to increase transmission between successive hosts. In intermediate fish hosts, previous research has measured increased frequency of conspicuous behaviors, decreased swimming performance, and reduced antipredator behavior, which would collectively increase the fish’s risk of predation. In ecosystems where this type of parasite increased trophic transmission (PITT) occurs, parasites can play a substantial role in food webs. In this study, I investigate how chronic versus acute exposure to the trematode Euhaplorchis sp. A. affects the antipredator behavior of the Gulf killifish Fundulus grandis. Using a fully crossed design, I examine how acute versus chronic exposure to infectious larval parasites (i.e., cercariae) alter the fish’s primary antipredator behavior, the fast-start escape response, which is a high-speed anaerobically fueled burst swimming behavior used primarily to evade attacking predators. Chronic parasite exposure had no significant impact on the reaction timing (i.e., latency) or kinematic performance (i.e., average turning rate and distance covered) of the fast-start escape response. Acute exposure reduced average turning rates, regardless of previous infection history, indicating a decline in agility in the presence of infectious cercariae. All fish used in this study were experimentally infected in the laboratory, so I also examined the factors influencing infection risk, by investigating how body size and sex influence infection intensity. Infection intensity increased significantly with body length and was significantly greater in males than females. Fundulus spp. are found in marsh habitats worldwide; this study aids in understanding the ecological role of parasite exposure in defining the ecological niche of these widespread fishes.

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