PHYSIOLOGY, BIOCHEMISTRY, AND TOXICOLOGY Comparative Total Activities of Digestive Enzymes in Different Gut Regions of the House Cricket, Acheta domesticus L. (Orthoptera: Gryllidae)

ABSTRACT The total luminal enzyme activity levels of carbohydrase (amylase, sucrase, maltase, trehalase), lipase, and protease were compared. Caecum, ventriculus, anterior hindgut, and posterior hindgut were assayed under the pH conditions in each region to determine the importance of each region for the digestion of food. The pH of each gut region was regulated and was not influenced by food. Food remained in the acidic (pH, 5.0) crop for 3—5 h, and most of the digestion of carbohydrates occurred there. No enzymes were secreted in the crop; rather, enzymes produced in the caeca were transported forward from the caecum into the crop. The proventriculus ground the food and slowly released the crop material into the ventriculus where it was buffered to a pH of 7.2-7.4. Most of the total protease activity occurred in the crop and ventriculus. Most of the absorption of digested food occurred in the relatively short ventriculus. It only required 30-50 min for the food to pass from the crop to the rectum. The hindgut or the contained bacterial symbionts produced some enzymes, mainly lipase, and some absorption of digest products, especially lipids, occurred in this region. KEY WORDS digestive enzyme, carbohydrase, house cricket DIGESTIVE ENZYMES are produced and distrib-uted in different regions of the gut; therefore, enzymes differ in type and amount. The amount of enzyme is determined as the total activity per total gut region per hour. Quantitative compari-sons of activity generally are assayed at the p