Tryptic and Chymotryptic Activities in Different Parts of the Gut of the Field Cricket Gryllus bimaculatus (Orthoptera: Gryllidae)

Abstract

Tryptic and chymotryptic activities of the field cricket Gryllus bimaculatus De Geer were assayed with benzoyl-L-arginine ethyl ester and N-benzoyl-L-tyrosine ethyl ester. In fed, but not in starved, crickets the contents of the foregut were acidic and those of other parts of the gut were alkaline. Both tryptic and chymotryptic activities reached maximal levels at pH 8.0, and only the caeca, ventriculus, and hindgut provided optimal pH conditions. Among the tissue homogenates, the highest activities of both enzymes were in caecal tissues. Tryptic activity was highest in the caecal lumen and chymotryptic activity was highest in the lumen of the ileum. The rectal lumen contained only very low levels of their activities. When the enzymic activities were assayed at the ambient pH of each gut region, the tryptic activity was still highest in the caecal lumen and the chymotryptic activities were equally high in the caecal and ileal lumen. Starvation for 5 d resulted in greater decreases of tryptic than chymotryptic activities in both the tissues and contents, and the foregut luminal activities of both enzymes were most severely affected.