Distinctive features of the alimentary canal of a fungus-feeding hemipteran, Mezira granulata (Heteroptera: Aradidae).

Hemiptera (Insecta) have specialized mouthparts for fluid feeding as well as distinctive midgut epithelia. The gut epithelia of Mezira granulata, a member of an unusual family of Hemiptera - the Aradidae - are described in this manuscript. Species of this family are thought to feed on fungi instead of plant or animal materials, as is more typical of the Hemiptera. The midgut lumen is lined by perimicrovillar membranes rather than by the peritrophic membranes formed by specialized midgut cells of stomodeal valves found at foregut-midgut interfaces in many insects. However, a stomodeal valve also occurs at the foregut-midgut boundary in these aradid bugs, and certain midgut epithelial cells located at the interface are specialized for secretion of an electron-dense extracellular matrix that fills the midgut lumen in the vicinity of the stomodeal valve. In addition to the distinctive cellular architecture of the apical (luminal) surfaces of midgut epithelial cells, luminal surfaces of the aradid hindgut epithelia are regionally differentiated into three regions with very different cuticles.