Unusual basement layer in the midgut of gammaridean Niphargus virei Chevreux (Crustacea, Amphipoda).

The basement membrane of the midgut and posterior caeca epithelium in the gammaridean amphipod Niphargus virei Chevreux, 1896 is made of an unusual structure. This basal lamina, properly called "basal layer", shows a dense sheet formed by a system of dense hexagonal plates connected by thin filaments. Histochemical studies and enzymatic reactions lead to the conclusion that these structures are proteinaceous, without collagenous protein, and embedded in a neutral polysaccharide matrix. The possible mechanical significance of these mesenteric structures is discussed.