Formation, properties and degradation of the peritrophic membranes of larval and adult fleshflies,Parasarcophaga argyrostoma (Insecta, Diptera)

Abstract

Parasarcophaga argyrostoma larvae continuously secrete a single, tube-like peritrophic membrane (PM), which has an electron-dense layer on the lumen side and a thicker chitin-containing electron-lucent part on the epithelium side. In the adult fleshfly, the secretion of PMs starts immediately after emergence. The initial part of the PMs is twisted and tight. The formation zone is folded with two separate secretory pads in which two tube-like PMs are formed continuously. The PMs are different, morphologically and with respect to their peripheral carbohydrate residues. The latter could be demonstrated with lectin gold conjugates. PM 1 consists of an electron-dense, chitin-free layer on the lumen side and a thicker part which contains chitin microfibrils in the matrix. PM 2 appears fluffy and has chitin microfibrils in its matrix, too. Chitin could be localized with WGA gold. Incubation of isolated PM 1 with lectin gold resulted in a peculiar pattern of bound lectins and gaps on the electron dense layer which otherwise appeared to be homogenous. Degradation of peritrophic membranes takes place in the hindgut. The cuticle of the anterior hindgut is studded with small teeth, which seem to be responsible for mechanical degradation of the peritrophic membranes into frayed pieces. This may be completed by the teeth on the rectal pads. From the appearance of the remnants of the peritrophic membranes it can be inferred that chemical degradation takes place in the hindgut.