Roles of Peritrophic Membranes in Protecting Herbivorous Insects From Ingested Plant Allelochemicals

摘要

Four mechanisms by which peritrophic membranes (PMs) po- tentially protect herbivorous insects from ingested allelo- chemicals are reviewed: adsorption, ultrafiltration, polyanion exclusion, and the capacity of PMs to act as antioxidants. Most of the research on the protective roles of PMs against ingested allelochemicals has focused on their impermeability to tannins. Adsorption of tannins by the PMs in grasshoppers may limit their permeability, but ultrafiltration of tannin complexes in the caeca is an alternative explanation. Polyanion exclusion does not explain the impermeability of caterpillar PMs to tannins (polyphenolate anions). Ultrafiltration remains the most likely mechanism by which tannins, and other tested allelochemicals, are retained in the endoperitrophic space. Al- though the pores in PMs are too large to impede the passage of most free allelochemicals, large allelochemical complexes are retained. Such complexes form in the gut fluid of caterpillars between tannic acid, proteins, lipids, and polyvalent metal cat- ions, and also in the gut fluid of grasshoppers (Melanoplus sanguinipes) between some amphiphilic allelochemicals (digi- toxin) and surfactant micelles. Further work is needed to ex- amine the role of PMs as antioxidants in vivo, such as their potential to bind catalytically-active metal ions. Arch. Insect Biochem.