Joseph Woodring

Insects are an extremely successful group of animals, primarily because they have over million of years evolved morphological and biochemical adaptations for virtually every possible food source. The variety of their mouthparts allows them to consume every kind of fluid or solids foods of both plant and animal origin. Surprisingly, the digestive enzymes of insects and vertebrates are quite similar in molecular structure and location in the digestive tract. Digestive enzyme synthesis, secretion and mechanism of digestion are basically similar in all animals. The control of digestive enzyme secretion in vertebrates is well understood, but the contral of enzyme secretion in insects remains a mystery. In my lab we are primarily interested in the physiology of digestion in insects, and especially with the regulation of secretion of digestive enzymes. We use the two-spotted field cricket as our lab animal because it is easy to rear and is large enough to easily dissect the digestive tract. 

Newly synthesized enzymes in insects are present as vesicles in the cytoplasm of the midgut epithelial cells. The enzymes are either continuously secreted from epithelial cells or released in response to food, however no one knows which method prevails. In the case of continuous secretion, the secretion rate would be determined only by the number and size of secretory cells. In the case of regulated secretion a specific component of the diet would dock onto an epithelial cell receptor, that then somehow induces the release of a specific enzyme.    

Insects are important members of all ecosystems. An understanding of the feeding and digestive processes of a species is a worthwhile goal, because this knowledge provides valuable insights into the adaptation of a species to its environment. In species where little or nothing is know we always start with a description of the morphology of the digestive tract. Next, we measure the activity ofthe major enzymes in the gut lumen, in homogenates ofthe . epithelium, and in the secretions of incubated gut regions. Finally, we determine the role of the amount and composition of the diet on the secretion of digestive enzymes.