Tegumentary ultrastructure (SEM) of preadult and adult Lobatostoma jungwirthi Kritscher, 1974 (Trematoda : Aspidogastrea)

Larval Lobatostoma jungwirthi Kritscher, 1974 (Trematoda: Aspidogastrea) pa rasitize the digestive gland of Heleobia parchappii (d'Orbigny, 1835) (Moll usca: Hydrobiidae) and, as adults, the posterior intestine of the chameleon cichlid Cichlasoma facetum (Jenyns, 1842) (Pisces, Cichlidae). Currently, L. jungwirthi is the only aspidogastrid reported from freshwater fishes in Argentina. Tegumentary structures of preadults and adults of L. jungwirthi were observed under scanning electron microscopy. In the preadult, 2 types of sensory receptors were observed: monociliate papillae of intermediate le ngth on the walls and crests of the ventral adhesive disc as well as on the disc periphery and oral lobules, and nonciliate dome-shaped papillae on th e crests of the ventral adhesive disc, neck, and oral lobules. In adults, o ther types of sensory receptors could be observed: in the posterior dorsal region, monociliate papillae with longer cilia than those found in the prea dult, and a multiciliate structure in the dorsal region at the posterior th ird of the body. This is the first record of a surface multiciliate recepto r in aspidogastreans. The pores of marginal glands were found only between the anterior alveoli.