A morphological study of the enteric valves of the Afrotropical Apicotermitinae (Isoptera: Termitidae)

Abstract

Soil-feeding termites are dominant members of the soil fauna in lowland tropical rainforests. As ecosystem engineers, they have a profound effect on their environment, particularly through modification of the vast quantities of soil that they ingest. There is growing evidence that the processing of the soil in the gut is influenced by the enteric valve--an extremely well-developed feature in the hindgut of the Termitidae, consisting of six ridges, variously armed with spines, teeth and scales. Although this valve has been extensively used in morphological work, little is known of its function. Scanning electron microscopy has been used in this study to better understand the three-dimensional structure of the enteric valve in the Afrotropical Apicotermitinae, a group in which these valves are everted into the following chamber of the hindgut. This configuration lends itself to scanning electron microscopy in a way that it does not in other soil-feeders, since in those species the armature is obscured within the gut lumen. It seems plausible that this structure is instrumental in filtering material through the gut in such a way that the coarse, organic-poor portion of the soil is channeled fast through the centre, while directing the fine, organic-rich portion to the edges for lengthier digestion of recalcitrant plant material. Thus, the enteric valve would appear to be important for the termites to survive on this nutrient-poor but super-abundant food resource.