Peritrophic matrix of the black fly Simulium vittatum: formation, structure, and analysis of its protein components.

The peritrophic matrix (PM) (same as peritrophic membrane) is secreted by the midgut epithelium of insects and completely surrounds the ingested food. The PM is likely to influence disease transmission by hematophagous insects. As a prelude to a more detailed examination of PM function, we report on morphological and molecular studies of the PM type 1 (PM1) from Simulium vittatum. The blood meal induces major changes in epithelial cell morphology: cells become flattened, microvilli decrease dramatically in number, and organelles redistribute in the cytoplasma. The PM1 forms within minutes of the blood meal. After 6 h the PM1 has reached its maximum thickness (approximately 13 microns) and strength. Two-dimensional gel electrophoresis reveals two major PM1-specific proteins of 66 and 61 kDa. Synthesis of these PM1 proteins is likely to be induced by the blood meal, since they are not detectable prior to blood feeding. The time course of accumulation and disappearance of the PM1 proteins closely correlates with the appearance and disappearance of the PM1 itself.