The peritrophic membrane of the gastropod Megathura crenulata: structure, composition, and site of formation

Abstract

Peritrophic membranes (PMs) are acellular layered structures secreted around ingested materials by the gut epithelium. Most studies on PMs have focused on those of insects and crustaceans due to their potential ability to block the movement of pathogens from ingested materials into the body, and their possible use as unique targets relevant to pest management. While PMs are known to occur in other taxa, their distribution is spotty and little is known about their role in these other species. The gastropod Megathura crenulata produces a true PM, which has a chitinous matrix that makes up nearly half its wet weight. Unlike arthropod PMs, which are released by delamination from the microvilli of their gut cells, the chitinous matrix of the M. crenulata PM is secreted from epithelial cells lining most regions of its gut. Although its mode of synthesis is unique, it may serve the same functions as proposed for other PMs, including regulating diffusion, binding metabolites, restricting protease activity, blocking pathogens, and providing lubrication. In arthropods, numerous proteins with chitin‐binding specificities have been identified, consistent with the proposed functions. Analysis of PMs in M. crenulata showed several integral proteins associated with the membrane, suggesting that the PM in this mollusc may be involved in complex functions like those seen in the arthropods.

Impact of weathered multi-walled carbon nanotubes on the epithelial cells of the intestinal tract in the freshwater grazers Lymnaea stagnalis and Rhithrogena semicolorata

“…One potential mechanism to protect epithelial cells in the intestinal tube and the digestive gland from mechanical or chemical damage is a peritrophic membrane (PM) (Sadava et al 2018 ). Although a well-described feature in insects and other arthropods, much less is known about PMs in molluscs (Peters 1969 ; Valk et al 2014 ). The PM surrounds the food bolus in the intestine and is made by protein and/or sugar fibres to form a filter-like structure.…”

“…Type I PM is constantly present in insects such as Dictyoptera, Coleoptera, Hymenoptera, Odonata, Orthoptera, Ephemeroptera and Phasmida. In molluscs, reports on PM are rare; a PM has been shown in the gastropod Megathura crenulata (Valk et al 2014 ). Therefore, PM filter functions may be crucial to understand the transport mechanisms of wMWCNTs in the lumen of L. stagnalis and R. semicolorata.…”