Proteolytic Gut Enzymes in Tipula caloptera – Interaction with Phenolics

We compared the proteolytic capabilities of the stream dwelling invertebrates Tipula caloptera Lw. (shredder) and Hexatoma sp. (carnivore) and the effects of pH and polyphenolics on enzyme activity. For T. caloptera, higher proteolytic activity was observed at a pH of 10, whereas for Hexatoma maximum proteolytic activity was observed at a pH between 8 and 9. At a pH of 10, neither leaf extract with high polyphenolic content nor tannic acid (up to 1 µg/ml) suppressed T. caloptera proteases. At a pH of 7, proteolytic activity of T. caloptera was significantly lowered by leaf extracts, and tannic acid. T. caloptera and Hexatoma sp. seem to differ in their digestive strategies. The proteinase activity of T. caloptera peaks at a highly alkaline pH, which is maintained in its midgut. It is therefore expected to be relatively unaffected by polyphenolics in leaves, which make up a major portion of its food. This problem is not encountered by the carnivorous Hexatoma larvae.