This collection of digeneans includes many pathogenic species. As is typical for the higher level taxa of Digenea, adults are quite diverse in appearance and the group is united by larval features.

Life Cycle

Adults tend to be found in the intestine or digestive organs of aquatic or semi-aquatic hosts. Most species produce sporocysts first and then rediae as the final stage in the molluscan first intermediate host. The cercariae encyst as metacercariae either on vegetation or in the mollusc that produced them, and they must then be eaten by their definitive host. The redia is notable because it can be considered a "top predator" within the mollusc. Often molluscs will be infected with several species of digenean, and echinostome rediae will prey on other species. They have actually been considered as a form of biological control of schistosomes, because the latter produce only a sporocyst stage which is non-motile and an easy prey!


The cercariae of this group have bodies that resemble the adult stage, consequently they differ considerably. However, all have simple tails. Rediae of this group have appendages. Adults tend to have spinous bodies, although the spines sometimes fall off after death and the body appears naked. The acetabulum is located in the anterior portion of the body.