L�PEZ, M.; BELDEN, L.K.*; MIRZA, R.S.; KIESECKER, J.M.; Pennsylvania State University; Virginia Polytechnic Institute and State University; Pennsylvania State University; Pennsylvania State University: Host-finding behavior in trematode cercariae (family: Teleorchidae)

Parasites rely on other organisms to complete all or a part of their life cycle. Therefore, the ability to locate hosts is paramount to their success. Digenetic trematodes primarily utilize freshwater mollusks as intermediate hosts. In addition, some utilize a larval amphibian as a secondary intermediate host. We were interested in whether trematode cercariae could actively locate an amphibian host. Using a test chamber with two discreet ends, we tested Teleorchidae cercariae collected from Physid snails for their ability to move towards an anesthetized tadpole versus an empty side. In addition, we tested their preference for tadpoles that were already infected with cercariae versus tadpoles that were uninfected. We also tested for a preference between tadpoles and salamander larvae. We found that cercariae preferentially moved toward the tadpole instead of the blank end of the chamber, which implies that they are able to actively locate a potential host in the environment. However, infection status of the tadpole did not seem to influence cercarial preference (although there was a slight trend toward moving to the uninfected tadpole) and there was no distinction made between tadpoles and salamander larvae. Based on these results, it appears that the Teleorchidae cercariae we tested may utilize some type of chemical cue to locate potential hosts in the aquatic environment.