These are parasites of all classes of vertebrates. Many species cause altered behavior in their intermediate hosts.
Adults live in the intestine of fish, amphibians, reptiles, birds and mammals. Crustaceans are the intermediate host. Paratenic hosts may be used.
Main longitudinal lacunar canals are lateral. Giant nuclei are absent. Cement glands in male are separate. There is one ligament sac in the female and it does not persist throughout life.