ULTRASTRUCTURE OF THE GUT CECAL EPITHELIUM OF PRICEA-MULTAE (MONOGENEA, POLYOPISTHOCOTYLEA)

Ultrastructural observations of the gut caecal epithelium of Pricea mu ltae revealed the presence of pigmented and non-pigmented digestive ce lls. The pigmented digestive cells were separated by a connecting sync ytium and appeared elongated, with numerous vesicles appearing toward the apical cell surface. They were characterised by granular inclusion s in the form of electron-dense pigments, which were eliminated by exo cytosis. These cells and their lamellar connecting syncytium were obse rved projecting into the gut lumen. Transverse sections of the gut epi thelium revealed intact portions of digestive cells lying in the lumen . Endocytosis at the apical surface of the pigmented digestive cells g ave rise to the formation of granular inclusions, which appeared as el ectron-dense pigments confined to lysosomal vesicles within the digest ive system. Electron X-ray microanalysis indicated these granules were primarily composed of iron, demonstrating that P. multae is a blood-f eeder. The connecting syncytium, while probably involved in a structur al, supportive role, may additionally function in the absorption of mi cromolecular nutrients from the host blood meal.