Structure and permeability of the peritrophic membranes of some small crustaceans

The permeability of the peritrophic membranes of some crustaceans was investigated by using dextran fractions unlabelled or labelled with the fluorescent dye FITC, colloidal gold particles with a diameter of 17 nm coupled with BSA, and unisphere latex particles as markers. The peritrophic membranes of Daphnia magna are permeable to dextrans with a molecular weight up to 2.000 kDa (ESR 31 nm), and to latex beads with a diameter of 130 nm. Latex beads with a diameter of 327 nm did not penetrate. The peritrophic membranes of metanauplii of Artemia salina are fully permeable for latex beads with a diameter of 70 nm, less permeable for those of 130 nm, and completely impermeable for beads with a diameter of 327 nm. Adults have nearly the same effective pore size of the peritrophic membranes as the metanauplii. The peritrophic membranes of Cyclops strenuus were permeable only to latex beads with a diameter of 70 nm. The peritrophic membranes of Gammarus pulex were permeated by latex beads with a diameter of 327 nm, whereas latex beads with a diameter of 542 nm were retained. The results demonstrated that the permeability of the peritrophic membranes of crustaceans is considerably greater than that of Diptera.