Abstract
We investigated the pattern of infection of Gammarus aequicauda (Amphipoda) with metacercariae of Levinseniella tridigitata (Trematoda: Microphallidae) in a natural lagoon. Prevalence was significantly higher in females than in males, whereas there was no difference between sexes in parasitic intensity. Despite the very large size of L. tridigitata metacercariae, the mean abundance increased with host size and in both sexes, suggesting that the accumulation of this parasite has no significant effect on host survival. Levinseniella tridigitata is known not to alter its host's behavior. Our results contrast with those obtained with other helminths that alter host behavior in order to favor their transmission to the definitive host.