The digestive system of adult carabid beetles : an ultrastructural and histoenzymological study

The morphological organization and the enzymatic equipment diversity of each digestive segment were studied by means of histology, electron microscopy and histoenzymology in seven carabid species : Carabus splendens, C. nemoralis, C. arvensis, C. problematicus, C. cancellatus, Abax parallelepipedus and Pterostichus melanarius. A particular function was attributed to each alimentary canal segment. The foregut is a mechanically functioning unit ensuring filtration and, in some cases, the site of temporary food storage. It is also the main site of food digestion, the digestive enzymes originating from regurgitated midgut fluid. The anterior region of the midgut plays a role in secretion and absorption processes, whereas the posterior one is the site of intracellular products storage, as well as of excretion and hydromineral regulation. The gastric caeca have a double function since they contain nests of regeneration cells and digestive glands. The hindgut disionic regulation. The fact that the digestive enzymatic equipment of carabids is well diversified (proteases, several polysaccharidases and oligosaccharidases) can be interpreted as a primitive character.