P. G. Department of Zoology, St. John's College, Palayamkottai, Tirunelveli-627002, Tamil Nadu, (India).
The house cricket, Gryllodes sigillatus (Walker), was reared on six formulated oligic diets with protein content in diet ranging from 11.97% (type I diet) to 14.21% (type II), 15.63% (type III), 21.52% (type IV), 24.32 (type V) and 28.67% (type VI) but all were isocalorific (17±1 J/mg). Substrate specific enzyme activity enhancement was observed in all diet fed crickets. The protease activity increased from 14 unit/gut/h in low protein type I diet (11.97%) to 19 in high protein type V diet (24.32%). With the increase in age and food consumption, in each diet 'group,a corresponding increase in digestive enzyme activity was observed. In type I diet, it was maximal in the penultimate (47 unit/gut/h) and last nymphal instar stage (51.5) and also in adult (59.95) than in early III instar nymphal stage (14.32). Enzyme distribution analyses revealed that enzyme activity commenced in foregut (amylase and invertase) and completed in mid gut (amylase, invertase, trehalase, cellulase, protease and lipase). The amount of protease but not carbohydrase increased with the increase in the level of protein in the diet. Gut protease activity increased from 60 unit/gut/h in type I diet to 66 in type VI diet in adult crickets. Elevated enzyme activity in adult crickets was due to adult feeding to compensate energy utilization for egg production.
