Morphology of the digestive system in the wood-feeding termite Nasutitermes takasagoensis (Shiraki) [Isoptera : Termitidae]

The morphologies of epithelial cells throughout the alimentary canal of the wood-feeding termite Nasutitermes takasagoensis (Shiraki) were examined. T he digestive tract consists of four principal portions, which are the foreg ut, the midgut, the mixed segment and the hindgut. The midgut epithelium is primarily composed of columnar cells and degenerative cells. Most columnar cells have one or more autophagic vacuoles at cell apexes, suggesting a ra pid turnover of the midgut cells. In the mixed segment, the mesenteric epit helium occupies half of the gut wall and the proctodeal epithelium covers t he remaining wall. Extensive invaginations of the basal membrane are charac teristic of the mesenteric columnar cells, suggesting active transport of a n ionic fluid. The hindgut can be divided into five segments, the first of which is a simple tube lined with a thick cuticle, termed the first proctod eal segment. The epithelium of the third segment, the paunch, consists of c uboidal cells, which are covered by multiple cuticular layers. The apical m embrane of these epithelial cells forms regular invaginations, suggesting t hat they have an absorptive function. In the anterior paunch, numerous spir ochetes are found adhered to the gut wall. Our observations indicate that t ermites such as N. takasagoensis appear to have developed structures that e nable more efficient interactions with intestinal microorganisms, particula rly by the elongation and differentiation of the hindgut and the creation o f the mixed segment.