EFFECTS OF PROTEASE INHIBITOR CONCENTRATION AND COMBINATIONS ON THE SURVIVAL, GROWTH AND GUT ENZYME-ACTIVITIES OF THE BLACK FIELD CRICKET, TELEOGRYLLUS-COMMODUS

Growth and survival responses were determined for the black field cric ket Teleogryllus commodus fed 6 different protease inhibitors (SBTI, W GI-1, POT-1, POT-2, BPTI and CpTI), either singly or in combination, a t a range of concentrations in diets containing 3 different levels of casein. Several inhibitors caused high levels of mortality at concentr ations as low as 0.1% (w/v) on diets with low or moderate casein. In a ll cases the efficacy of the protease inhibitors in reducing cricket g rowth was strongly influenced by the level of dietary casein as well a s by the concentration of the inhibitor. POT-2 and SBTI were particula rly effective. Two-way combinations of protease inhibitors caused sign ificant mortality and reduced growth as effectively as the best single inhibitors at all dietary casein levels. A synergistic effect was obt ained from the combination of POT-1 (binds strongly to SAAPLpNA hydrol ysing enzyme) and WGI-1 (binds strongly to trypsin). A time-series stu dy using POT-2 showed that this inhibitor caused continual suppression in the activity of the digestive endopeptidases trypsin and SAAPLpNA hydrolysing enzyme, but no reduction in the activity of the exopeptida se leucine aminopeptidase. Increased levels of enzyme inhibition at th e higher POT-2 concentration were directly reflected in the feeding tr ials where greater growth suppression was also observed.