Metacercariae

Cercaria (plural: cercariae)

Species of family Syncoeliidae have mesocercariae or metacercariae that are not encysted and can be free floating, but details of the early stages of the life cycles of these marine parasites are not known. Bony and cartilaginous fish are the definitive hosts within at least the gills, oral cavity or skin, and crustaceans like krill and copepods can be paratenic or possibly intermediate hosts. Metacercariae of certain species, such as Copiatestes filiferum, have long filamentous structures termed byssal filaments, which in C. filiferum have been reported to foul the feet of white-faced storm petrels and cause snagging-related mortality in this accidental host after the metacercariae dry out and form hardened connections between the legs.