The life-cycle of Echinostoma friedi n. sp (Trematoda : Echinostomatidae) in Spain and a discussion on the relationships within the 'revolutum' groupbased 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 (Ga stropoda: Lymnaeidae) serves as the natural and experimental first intermed iate host and L. corvus and Gyraulus chinensis (Gastropoda: Planorbidae) as experimental first intermediate hosts. These, and Physella acuta (Gastropo da: Physidae), also serve as second intermediate hosts. Adult worms, posses sing 37 collar spines, were obtained from naturally infected Rattus norvegi cus and experimentally from albino rats, golden hamsters and chickens. Mice were not suitable experimental definitive hosts. E. friedi differs from th e 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 compar ison of these species may be carried out on the basis of the number of sens illa in the clusters CIII V-1, CIII V-2 (or CIII V-1 + CIII V-2), CIV DL an d UVb. These clusters appear adequate to establish taxonomic relationships between different species within the `revolutum' group.