Summary: Trematodes are abundant parasites that significantly influence community structure and energy flow in estuarine ecosystems. Their effects on hosts include behavioral modification, castration, tissue degradation, and mortality. Trematodes are also important indicators of ecosystem health, because their indirect life cycles (which require two to three hosts) depend upon a diverse and healthy community. The indirect life cycles of trematodes also include two free-living, host-seeking larval stages. The swimming behaviors of these stages, and the environmental conditions that influence them, are critical factors that determine a parasite’s ability to maintain connectivity between hosts.
In New England estuaries, nine trematode species parasitize the abundant Eastern Mudsnail (Tritia obsoleta) as a first intermediate host. Trematodes disperse from the snail as swimming or crawling larvae called cercariae. Cercariae target many species from various taxa as their second intermediate host, including fish, bivalves, and worms. Some life cycles of these trematode species have been described in laboratory studies, but the dispersal potential, transmission dynamics, and infectivity of cercariae to second intermediate hosts in the wild are largely unknown. My project uses a combination of field and laboratory experiments to understand how larval behavior, host distribution, and features of the estuarine environment determine when and where infection occurs. In particular, I will use bivalves in aquaculture as focal host species for their importance to the ecology, culture, and economy of New England. The aim of this research is to provide a mechanistic understanding of how larval behavior and the environment contribute to parasite connectivity, and apply this understanding to assessing risk in different aquaculture systems.
Project Title: Investigating the effect of salinity on mud crab parasite communities
Principal Investigator(s): Carolyn Tepolt, Zachary Tobias
Affiliations: Woods Hole Oceanographic Institution, Department of Biology
Summary: The flatback mud crab, Eurypanopeus depressus, is a common estuarine crustacean from the Gulf of Mexico to New England. It is affected by a range of parasites that may vary with the environment. The goal of this project is to characterize the parasite communities within E. depressus along salinity gradients throughout the Northeast. Studies have shown that some crab species may use low salinity water as refuges from marine parasites. We will investigate how these crabs may have adapted to low salinity in response to pressures from parasitism using ecological field surveys and transcriptomic analyses.
Project Title: Trematode Parasites of Tritia obsoleta
Principal Investigator(s): Lauren Dykman
Summary: I am surveying populations of the Eastern Mudsnail (Tritia obsoleta) in Waquoit Bay to locate snails that are parasitized by trematodes. These parasitic worms use three hosts in their life cycle, the first being the Mudsnail. Parasites live in the snail’s gonads and repeatedly shed clones into the water. I am collecting groups of snails and holding them in the lab for 24 hours to see if they shed parasites. I keep infected snails in order to study the behavior of their parasites. All uninfected snails get returned home to Waquoit Bay the following day.
Once parasites are shed from the snail, they have a limited amount of time to find their next host before they die. For the species that infect the Eastern Mudsnail, I want to learn how long they survive outside their host, what is their maximum swimming speed, what distance can they travel, and whether they respond behaviorally to host cues. All these measurements give a better idea of the likelihood of encountering hosts. This work is directed towards understanding population connectivity on both a small scale, and between distant estuaries along the Eastern Seaboard.