Plagioporos sinitsini (Digenea : Opecoelidae): A one-host life cycle

Adult Plagioporus sinitsini occur within daughter sporocysts voided with th e feces of prosobranch snails Elimia symmetrica in Basin Creek, North Carol ina. These worms produced eggs containing active miracidia while still in t he snail. Adults in snails and adults in rosyside dace, Clinostomus fundulo ides, collected from the same stream were indistinguishable morphometricall y. Adults in snails develop from cotylocercous cercariae sequestered in dau ghter sporocysts that pass through the metacercaria stage. These observatio ns, and previous study in Michigan, suggest that the life cycle of P. sinit sini has 3 potential pathways, i.e., a 3-host life cycle involving mollusca n, arthropod, and piscine hosts, a 2-host life cycle involving only mollusc an and piscine hosts, and a 1-host life cycle involving only the snail host . The truncated Life cycles do not appear to be the result of paedomorphosi s.