Meeting Abstract

P3.134  Sunday, Jan. 6  The Peritrophic Membrane of the Giant Keyhole Limpet MARTIN, GG*; VALK, J; Occidental College, Los Angeles; Occidental College, Los Angeles gmartin@oxy.edu

Peritrophic membranes are acellular wrappers secreted by the gut epithelium around ingested materials and persisting to package fecal pellets. They may serve to protect the gut from abrasive items such as sand grains, protect against pathogen penetration, and may bind enzymes related to digestion. Peritrophic membranes are most common and most thoroughly studied in insects and to a lesser degree in crustaceans. They are barely mentioned in mollusks aside from basic descriptions by Peters (1992). We have observed transparent peritrophic membranes up to 7cm long extending from the dorsal shell hole in the giant keyhole limpet Megathura crenulata. A limpet will produce 1-2 membranes per week whether fed or not. They are composed of chitin based on 1) their insolubility in concentrated KOH, 2) staining with PAS and the lectin WGA which is specific for n-acetyl-glucosamine, the monomer of chitin, 3) digestion in chitinase but not protease, cellulose or cellulase. They are secreted by the distal third of the intestine although these epithelial cells do not show morphological features distinct from adjacent cells in anterior regions of the gut. Electron microscopy reveals a fibrillar network which seem to block penetration of materials larger than 0.5 um. Clean peritrophic membranes from starved animals were incubated with calcofluor, SDS, guanidine HCl, urea, and Congo red dye, agents shown to detach associated protein from membranes in insects. We will present preliminary attempts to identify these proteins by SDS-PAGE and Western blot analysis and compare them to proteins associated with membranes produced in other taxa.