Physiological effect of sugars on various digestive enzymes ofSpodoptera littoralis larvae

Summary Feeding of Styropor lamellae treated with 0.25 M maltose, sucrose, raffinose or melezitose byS. littoralis larvae induced amylase activity to 5–6 fold and invertase and protease activity to 2–3 that of the control. Melibiose induced amylase activity to about 4-fold and invertase and protease activity to 188% and 173%, respectively, that of the control. -lactose stimulated the various digestive enzymes to various extents; cellobiose had practically no effect. Glucose and fructose induced the various digestive enzymes to about the same level but to a much higher extent than galactose.The feeding rate of the various sugar compounds except maltose, correlates well with their stimulating activity on the digestive enzymes. Maltose, which induced the larval digestive enzymes to about the same level as that of sucrose, elicited a considerably lower feeding response. The excretion index of sugars stimulating digestive enzymes and eliciting a feeding response, such as maltose, sucrose, raffinose and melezitose, is considerably lower than that of the other sugars.In a comparative test, sucrose, maltose and raffinose induced the various digestive enzymes to about the same level as their equivalent monosaccharide components. However, -lactose and cellobiose, which have the same components as melibiose and maltose but differ in their configuration, affect the various enzymatic systems weakly.Contribution from The Volcani Center, Agricultural Research Organization, Bet Dagan, Israel. 1972 Series, No. 2171-E.Definitions. Feeding response: express the intake of sugar plus insert Styropor carrier. Excretion index: ratio between weight of fecal pellets and Styropor lamellae consumed.The authors wish to thank Mr. K. R. S. Ascher for fruitful discussions, Dr. A. Genizi for statistical analysis of the results, Mrs. Sara Yablonski and Mrs. Shulamit Cohen for skillful technical assistance, and Mrs. Shoshana Hadad for insect rearing.