The ultrastructure of the fore-gut of the redia of Parorchis acanthus Nicoll (Digenea: Philophthalmidae) from the digestive gland of Nucella lapillus L

Abstract

SUMMARYThe fore-gut of the redia of Parorchis acanthus is ingestive in function. It consists of a buccal cavity, suctorial pharynx and an oesophagus divided into anterior and posterior regions. The syncytial lining is continuous with that covering the body surface, except for the posterior region of the oesophagus which is lined by a separate syncytium. This latter has different cytoplasmic inclusions and the unusual feature of a single ventral nucleus in the outer cytoplasmic epidermis. Intrinsic and extrinsic muscles are responsible, respectively, for the fairly rapid passage of food through the fore-gut and for support. Secretion bodies in the epidermis are probably discharged into the lumen and pass with food into the intestine where they may be involved in extracellular digestion. Young rediae feed mainly by mouth while older, immotile rediae absorb nutrients mainly through the body surface.