The life-cycle of Echinostoma friedi n. sp. (Trematoda: Echinostomatidae) in Spain and a discussion on the relationships within the `revolutum' group based on cercarial chaetotaxy

The morphology of the different stages and life-cycle of Echinostoma friedi n. sp. are described and figured. The freshwater snail Lymnaea peregra (Gastropoda: Lymnaeidae) serves as the natural and experimental first intermediate host and L. corvus and Gyraulus chinensis (Gastropoda: Planorbidae) as experimental first intermediate hosts. These, and Physella acuta (Gastropoda: Physidae), also serve as second intermediate hosts. Adult worms, possessing 37 collar spines, were obtained from naturally infected Rattus norvegicus and experimentally from albino rats, golden hamsters and chickens. Mice were not suitable experimental definitive hosts. E. friedi differs from the most closely related species in the `revolutum' group mainly in terms of several morphological and biological features of the life-cycle stages and in its cercarial chaetotaxy. The chaetotaxy patterns of the species of the `revolutum' group are analyzed and the results show that a taxonomic comparison of these species may be carried out on the basis of the number of sensilla in the clusters CIII V₁, CIII V₂ (or CIII V₁ + CIII V₂), CIV DL and UV_b. These clusters appear adequate to establish taxonomic relationships between different species within the `revolutum' group.