|Light and electron microscope studies of the redia of Parorchis acanthus Nicoll|In: Parasitology. Cambridge University Press: London. ISSN 0031-1820, more
Nucella lapillus (Linnaeus, 1758) [WoRMS]; Parorchis acanthus (Nicoll, 906) Nicoll, 1907 [WoRMS]; Marine
Young and old rediae of Parorchis acanthus Nicoll, from the digestive gland and gonad of Nucella lapillus (L.) have been described. The young redia has an anterior collar-like fold and mid-ventral birth papilla the movements of which are controlled by a special arrangement of muscles. The birth papilla is ‘solid’ but in older rediae is replaced by a pore. The pharynx is of fairly uniform size irrespective of the size of the redia and the intestine, in the young redia, is relatively much larger than in the older redia which facts suggest that relatively more food may be absorbed by the mouth in the young stage. The redia cavity develops as a slit in the central cell mass. As it enlarges the intestine remains close to the dorsal wall and developing embryos are carried, among the cells, towards the surface dropping into the cavity, later, to complete their development. Up to fifty-five cercariae may be present in a redia. Simple nervous and excretory systems are present.