Trematode infection alters the antipredator behavior of a pulmonate snail

TitleTrematode infection alters the antipredator behavior of a pulmonate snail
Publication TypeJournal Article
Year of Publication2003
AuthorsBernot, RJ
JournalJournal of the North American Benthological Society
Pagination241 -248
Accession NumberKNZ00871
Keywordsantipredator behavior, cercariae, habitat use, parasitism, Physa integra, trematodes

Parasites can alter the behavior, life history, and morphology of their host. Many trematodes parasitize freshwater pulmonate snails, resulting in a reduction or the elimination of reproduction in those individuals. However, parasite effects on freshwater snail behavior are unclear. I measured trematode infection rates, size, and covered habitat use of the freshwater pulmonate snail Physa integra in a field survey of streams and ponds on Konza Prairie Biological Station. Then, in a laboratory experiment, I tested the hypothesis that behavioral decisions under the risk of predation differed between infected and uninfected P. integra. Infection rates ranged from 2% to 53% overall, but varied between snail size class and site of collection. Significantly fewer infected (7%) than uninfected P. integra (29%) were found under cover, but there was no difference in use of cover between snails infected with Paramphistomidae and Cathaemasiidae trematodes. A significantly greater proportion of larger snail size classes were infected than smaller size classes. In the laboratory experiment, habitat use by P. integra depended on predator presence and infection status. Significantly more uninfected snails used covered habitats in the presence of creek chub (Semotilus atromaculatus) than in the presence of crayfish (Orconectes nais) or in the absence of a predator. Significantly more uninfected snails used near-surface habitat in the presence of O. nais than in other treatments. However, in the presence of S. atromaculatus <20% of infected snails used cover compared to 60% of uninfected snails. Near-surface habitat use and crawlout behavior were also significantly higher among infected snails in crayfish and no predator treatments, suggesting that infected snails use near-surface habitats even when under predation risk. More detailed knowledge of this trematode–snail system is necessary, however, to determine if differences in habitat use between infected and uninfected snails is an adaptive manipulation of snail behavior by trematodes. Nevertheless, these results indicate that infection status affects the behavior of P. integra and may alter species interactions in freshwater benthic communities.