ECHINOSTOMA REVOLUTUM-INFECTED HELISOMA TRIVOL VIS TO ROMAINE LETTUCE (LACTUCA SATIVA LONGEFOLIA)

The chemoattraction of uninfected planorbid snails, Helisoma trivolvis, and those infected with larval stages of the trematode, Echinostoma revolutum, to boiled romaine lettuce (Lactuca sativa longefolia) was studied for 1 hr in Petri dish cultures containing pond water. Snails that contacted the lettuce were considered attracted. Snails infected with E. revolutum larvae were not significantly attracted to the lettuce, whereas un- infected snails were. For uninfected snails, the hydrophilic lettuce fraction elicited a significantly greater total contact time than the lipophilic fraction. Uninfected snails responded by chemoklinotaxis within 2.5 cm of the lettuce.