Localization of Sugar Components of Glycoproteins in Peritrophic Membranes of Larvae of Diptera (Culicidae, Simuliidae)
Dörner, Renate; Peters, Werner
In the cardia of larvae of Aedes aegypti Linnaeus 1758, Anopheles stephensi Liston 1901, Culex pipiens fatigans Wiedemann 1828, and Odagmia ornata Meigen 1818a single, tube-like peritrophic membrane is formed continuously which extends through the whole midgut and hindgut. Its fine structure differs in the genera which were investigated. The morphological differences are paralleled by biochemical differences which could be visualized with lectins labelled with colloidal gold as an electron dense marker. Either peritrophic membranes or midgut epithelium or ultrathin sections of peritrophic membranes were incubated with lectin-gold conjugates. Specificity of binding could be determined by competition with the respective sugars. N-acetylglucosamine und N-acetylgalactosamine residues were found on both sides of the peritrophic membrane of these species. Fucose residues were localized only on the epithelium side of the peritrophic membrane of larvae of A. aegypti. The midgut epithelium of all species did not bind any of the lectins tested. Gel electrophoresis of the peritrophic membranes of blackfly larvae, Odagmia ornata, showed protein / glycoprotein bands with apparent molecular weights of 140, 130, 75, 63, 54, 22, 18, 16 and 12 kDa. Glycoproteins with specificity for soy bean agglutinin (SBA)-gold, which binds to N-acetyl galactosamixne, with apparent molecular weights of 22, 18, 16 and 12 kDa could be demonstrated on nitrocellulose blots.