Functional morphology, ecology and physiology of the digestive system
Principal Investigator: Matthias W. Lorenz
Energy acquisition, storage and mobilisation are prerequisites for whole-animal performance. Since the acquisition and digestion of food stand at the very beginning of this metabolic chain, any traits that are involved in food consumption and processing will significantly influence an animals’ performance. In crickets, the digestive system is optimised to digest diets rich in complex carbohydrates, whereas lipid-rich diets cause severe problems, as we showed recently. On the other hand, the cricket fat body stores huge amounts of lipids but only very small amounts of glycogen. Crickets, therefore, have to synthesise lipids from a carbohydrate-rich diet. However, we showed that the fat body does not effectively use sugars as a substrate for lipid synthesis; instead, short chain fatty acids (SCFAs; acetic acid in particular) are very rapidly converted into lipids. An extoperitrophic ileal pouch in the cricket gut contains vast numbers of bacteria that are held in place by feathery bristles arising from the cuticular lining of the finger-like invaginations of the ileal wall. It is known that bacteria in the cricket gut produce SCFAs from dietary complex carbohydrates. We suggest that these SCFAs are taken up via the large surface of the ileal invaginations and are transferred into the haemolymph where we recently found comparatively high concentrations of SCFAs. These can be used by the fat body to synthesise the immense lipid stores that are later mobilised to fuel flight or egg production. Consequently, we are highly interested in the functional relationship between the cricket and its gut bacteria and in the coevolution of this system.