Morphology of the rediae of Echinostoma paraensei (Trematoda: Echinostomatidae) from its intermediate host Lymnaea columella (Mollusca, Gastropoda).

The morphology of the rediae of Echinostoma paraensei obtained from Lymnaea columella was studied using light, scanning and transmission electron microscopy. The measurements of the mature rediae differ from those described originally, and the taxonomic importance of the ambulatory buds and papilliform process is discussed. Uniciliated papillae were observed in the mouth region. The birth papilla is a bulb-like structure, well defined at the anterior end of the body of the rediae, which opens through a split. There are no microvilli in the tegument surface of the larvae, but numerous tegumental folds, varying according to the contraction of the body of the rediae. The outer syncytial layer is located on a thick basal lamina below which the circular and the longitudinal muscle fiber layers are located.