High performance thin-layer chromatography-densitometry was used to characterize and quantify free sterols and other lipids in Biomphalaria glabrata snails infected with Schistosoma mansoni and subjected to crowding. Observations were made on a non-crowded population (15 snails per culture) and a crowded population (50 snails per culture) of infected snails. Each culture contained 800 mL of artificial spring water, and snails were maintained at 25 ± 1oC and fed romaine lettuce ad libitum. After 4 weeks of culture, the infected snails were necropsied, and the digestive-gland gonad complex (DGG) of each snail was extracted in chloroform-methanol. Lipids were separated on 10 x 20 cm Analtech channeled HPTLC-HLF silica gel glass plates with a preadsorbent zone. The mobile phase petroleum ether-diethyl ether-glacial acetic acid (80:20:1) and 5% ethanolic phosphomolybdic acid detection reagent were used to analyze lipids in the DGG of each snail. Quantitative densitometric analysis was performed using a CAMAG TLC Scanner 3 with the tungsten light source set at 610 nm for neutral lipids. Free sterols and free fatty acids were the major lipids found in both crowded and non-crowded infected snails. Significant differences (ANOVA, P<0.05) were found in the free sterol fraction of the above described snail populations. Our findings indicated that snail crowding as described in our experiment caused a significant decrease in the free sterol content of the DGG of infected B. glabrata.
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