Structure and function of the peritrophic membranes of copepods.

Abstract

Peritrophic membranes are formed in all the 25 species examined. The peritrophic mem-branes of free-living and commensal notodelphyoid copepods are formed in the whole region of the mid-gut, whereas they are formed in the posterior region of the mid-gut in some cyclopoid associates of marine bivalves and parasitic copepods. The peritrophic membranes of free-living copepods are generally thicker than those of parasitic copepods. A chitosan test and histochemical and ultrastructural examinations revealed that the peritrophic membranes of free-living Tigriopus and parasitic Panaietis consist of chitinous microfibrils arranged in a disperse texture and a ground substance containing acid mucopolysaccharides and proteins, and chitinous microfibrils of Tigri-opus are much thicker than those of Panaietis. In Lernaea, faecal pellets are produced at conside-rably regular intervals. On the basis of these findings some possible roles of the peritrophic mem-branes of copepods are discussed.