SNAIL-HOST-FINDING BY MIRACIDIA AND CERCARIAE - CHEMICAL HOST CUES

Snails act as intermediate hosts in trematode life cycles, and many st udies have dealt with the question of how miracidia, mainly of schisto somes, find and recognize their snail hosts. However, the published re sults on the chemical snail host cues that attract miracidia of Schist osoma mansoni have been contradictory. Here, Wilfried Haas, Bernhard H aberl, Martin Kalbe and Martina Korner review data that indicate that macromolecular glycoproteins are the attractants, and that schistosome miracidia can distinguish between snail strains during their chemo-or ientation towards the hosts. in echinostome life cycles gastropods als o act as second intermediate hosts and are actively invaded by cercari ae. However, these cercariae approach their snail hosts with types of chemo-orientation that differ from those of miracidia, and they respon d to small molecular host cues.