Phytosterol metabolism and absorption in the generalist grasshopper, Schistocerca americana (Orthoptera : Acrididae)

A series of experiments, using GLC, RP-HPLC, and GC-MS techniques, were per formed to examine the metabolic fate and absorption of different dietary st erols in the grasshopper Schistocerca americana. In the first experiment, g rasshoppers were reared on diets containing different sterols presented sin gly. Cholesterol was the dominant tissue sterol recovered from cholesterol and "soybean sitosterol" fed grasshoppers but among the grasshoppers fed di ets with stigmasterol and spinach sterols (both unsuitable for growth and d evelopment), the amount of cholesterol :recovered was not different from th at of newly hatched grasshoppers. In the second experiment, grasshoppers we re given diets containing mixtures of soybean sitosterol and stigmasterol a nd the metabolic fate of these dietary sterols was recorded. Results from t his experiment suggest that the presence of an unsuitable dietary sterol do es not interfere with cholesterol production from sitosterol. They also dem onstrate that large quantities of unmetabolized dietary sterols with C-24 e thyl groups are recovered from grasshoppers fed diets containing stigmaster ol. Finally, tissue sterol profiles of grasshoppers with and without their midguts were compared. Results suggest that the midgut is the major tissue where unmetabolized dietary sterols accumulate. How these sterol metabolic constraints impact development and survival is discussed as well as the imp act they might have on grasshopper feeding behavior. (C) 1999 Wiley-Liss, I nc.