The intestine of Triatoma infestans. II. The surface coat of the midgut

The apical surface of the midgut epithelium in fasted Triatoma infestans shows a striated border covered by a surface coat. The electron microscope demonstrates that the surface coat, which has a tubular plexiform structure, is at least four times the height of the microvilli. A trilaminar membrane thinner than the cell membrane covers the apical surface of the epithelial cells and projects as tubular expansions into the lumen of the intestine. The trilaminar membrane ensheathes each microvillus. The intervillus space is occupied by a meshwork of septa continuous with the trilaminar membrane. Cytochemical techniques suggest that the extracellular coating contains glycophospholipids and acid phosphatase.