Formation and Composition of the Peritrophic Membrane in the Sand Fly, Phlebotomus perniciosus (Diptera: Psychodidae)

Abstract

The secretion, morphology, and chemical composition of the peritrophic membrane was studied in the sand fly, Phlebotomus perniciosus Newstead. The membrane was secreted from the entire midgut epithelium. An electron-dense fine granular secretion, possibly chitin, was present along the length of the microvilli immediately until 24 h after feeding. From 12-48 h, an electron-lucid coarse granular component, possibly protein, was also secreted from the microvillar surface. By light microscopy, the mature 36-h membrane characteristically consisted of a dark anterior cap and posterior open ring, with a transparent intervening membrane and anterior plug. Ultrastructure of the fully formed membrane at 24-48 h was highly variable. Undifferentiated membranes appeared as a single electron-lucid layer; differentiated membranes were more complex, sometimes two-layered, containing electron-lucid and -dense fibers and granules. Results of binding to succinylated wheat germ agglutinin, histochemistry, and amino acid analysis indicated that the membrane was composed of chitin, glycoprotein, and protein. Eighteen amino acids were identified in membrane proteins; aspartic-glutamic acids (and amides), serine, glycine, and lysine (45% by weight) may be important in cross-linking membrane components.