Pairing and aggregation ofAmblosoma suwaense(Trematoda: Brachylaimidae) metacercariaein vitroand partial characterization of lipids involved in chemo-attraction

Abstract

SUMMARYHistochemical and thin-layer chromatographic (t.l.c.) analyses were made on neutral lipids in the free (unencysted) metacercariae ofAmblosoma suwaense(Brachylaimidae). As determined by t.l.c. the major neutral lipid fractions in metacercariae removed directly fromCampeloma decisumsnails were free sterols and sterol esters. Metacercariae incubated for 1 h at 37±1° C in sterile Locke's solution released mainly sterol esters and a lesser amount of free sterols into the medium. As determined by Oil Red O (ORO) staining, metacercariae accumulated neutral lipid in the intestinal caeca during incubation and the excretory system was ORO negative. Behavioural studies showed that metacereariae paired and aggregatedin vitroand were attracted to lipophilic but not to hydrophilic worm products. Following t.l.c. preparative analysis it was demonstrated that metacercariae were attracted to sterol ester worm products but not to free sterol products.