Effect of intake of food and inert substances on the midgut invertase activity in the larvae of Utetheisa pulchella Linn

摘要

The effect of intake of food, distilled water and moistened filter paper on the secretion of invertase [beta-fructofuranosidase] in the midgut of fifth instar larvae of U. pulchella was studied. In the starved larvae, the intake of one meal of usualfood for a short duration (5 min) did not cause any appreciable increase in the secretion of beta-fructofuranosidase. The intake of several successive meals and the continuous presence of food in the midgut enhanced the invertase secretion. It is suggested that continuous feeding is an important factor to stimulate the secretion of digestive enzymes. When the starved larvae consumed distilled water or moist filter paper, the midgut showed enhanced secretion of beta-fructofuranosidase. Besides the chemical stimuli by the food material (secretogogue), the physical stimuli caused by the tasteless substances were also important factors in stimulating the midgut for beta-fructofuranosidase secretion.