Thin-layer chromatography and histochemistry analyses of neutral lipids in Helisoma trivolvis infected with four species of larval trematodes

Thin-layer chromatography (TLC) and histochemistry studies were done on the neutral lipid content of the digestive gland gonad (DGG) complex of Helisoma trivolvis infected with four species of larval trematodes. Two of the species, Ribeiroia sp. and Zygocotyle lunata, contained rediae, and the two others, Spirorchis sp. and an armatae xiphidiocercaria, contained sporocysts. The DGG infected by each species had its own distinct neutral lipid profile as determined by TLC. All profiles differed from that of the uninfected DGG. Densitometric TLC studies showed some quantitative differences in free sterols in infected versus uninfected DGGs. Visual observations of the chromatograms showed that all four species caused a marked elevation in the triacylglycerol fraction in the DGG as compared with the uninfected controls. Oil Red O (ORO) histochemistry studies showed that levels of neutral lipids were increased in the DGGs of infected versus uninfected samples. These histochemistry studies showed a variable distribution of neutral fat, ranging from its absence in the cercariae of Z. lunata and the armatae xiphidiocercaria to ORO-positive droplets in the excretory system of Ribeiroia sp. Rediae and sporocysts contained ORO-positive material in the body wall and in the space between cercariae. Received: 8 August 1997 / Accepted: 6 November 1997