Date of Award


Document Type


Degree Name

Master of Science (MS)


College of Science and Mathematics




Appropriate host selection by parasites is critical for ensuring offspring survival, optimal feeding location, and protection from predators. Leeches (Placobdella spp.) are known to parasitize bottom-dwelling turtle species more frequently than basking turtle species, but it is not known whether this bias is evolutionarily advantageous. I tested two potential factors that could influence host selection by leeches: differential chance of encounter due to habitat usage, and chemosensory bias of leeches toward bottom-dwelling species. I first confirmed that Chrysemys picta (Eastern painted turtle, a basking species) and Sternotherus odoratus (common musk turtle, a bottom-dwelling species) in Lake Wapalanne in Sussex County, New Jersey have different parasite loads under natural conditions. Leech loads varied seasonally in both species, but were consistently higher in musk turtles. In a controlled environment where the leeches had the same chance of encountering each turtle species, more leeches {Placobdella spp.) parasitized musk turtles than painted turtles. However, when presented with only turtle chemical cues in choice trials, results were mixed. When they were presented with a choice of either a turtle or no scent, they were more likely to go towards the turtle, regardless of which species was presented. However, when they were presented with both species of turtle the leeches were more likely to move than when no scent was present, but they showed no species preference. Thus the basis for the preference observed in the encounter trials is still unresolved, and may involve other cues beyond chemosensory stimuli. This could mean other factors such as turtle behaviors are playing into their decision-making process, or that turtle species differ in their ability to avoid or remove parasites.

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