[Superficial argentophilic structures of miracidia and cercaria of Paramphistomum leydeni Nasmark 1937].

The life cycle of Paramphistomum leydeni Näsmark, 1937, is carried out in the laboratory. Adults were obtained from the rumen of a naturally infected Bos taurus in Czechoslovakia. Laboratory-reared Planorbis planorbis experimentally infected shed the first cercariae two months after exposure to miracidia. Argentophilic structures in miracidia and cercariae are described. In miracidia, these structures are similar to those previously described from species of Paramphistomum: P. togolense, P. phillerouxi, P. daubneyi, P. microbothrium. They differ, however, from those of Calicophoron calicophorum. In cercariae, argentophilic structures have some features in common with those of the species of Paramphistomum mentioned above, especially at the levels CII and AM V, but the very peculiar acetabular chaetotaxy allows us to distinguish P. leydeni from these species. Thus, each species can easily be differentiated from the related species; moreover the genus Paramphistomum as characterized by Näsmark (1937) appears to be justified.