Chemoattraction of

High performance thin-layer chromatography (HPTLC) was used to analyze the lipophilic excretory-secretory (ES) products of Echinostoma trivolvis rediae. These products were free sterols at a concentration of 0.83 ± 0.03 μg/100 ml and a lesser amount of free fatty acid that was not quantified. Preparative layer chromatography (PLC) was used to obtain the free sterol and free fatty acid fractions of redial ES products, and silica gel squares containing these lipids were tested against single rediae in a Petri dish bioassay. Rediae were significantly attracted to squares containing either free sterol or free fatty acid. HPTLC was also used to analyze the major lipid fractions in the redial bodies, which were free sterols, phosphatidylcholine (PC), and phosphatidylethanolamine (PE). The major wet weight percentage ± SE (n = 3) of free sterols was 2.59 ± 0.16 and for PC and PE was 0.01 1 ± 0.002 and 0.010 ± 0.002, respectively