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

Abstract Peritrophic membranes ( PM s) are acellular layered structures secreted around ingested materials by the gut epithelium. Most studies on PM s 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 PM s 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 PM s, 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 PM s, 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 PM s 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.