Proteocephalus

Adults live in the intestine of freshwater poikilotherms, primarily fishes. Gravid proglottids are shed and eggs are liberated. They hatch in fresh water to release a coracidium. Copepods eat the coracidium and the oncosphere within it is released. The oncosphere uses hooks to penetrate into the body cavity and develop into a procercoid. A fish second intermediate host eats the infected copepod and the parasite migrates into the tissues and develops into a plerocercoid.

When a definitive host ingests infective plerocercoids the life cycle is complete. If a definitive host ingests immature plerocercoids, they will migrate into its tissues and complete their development to an infective plerocercoid. They will not mature in that host but are capable of maturing if it is eaten by yet another suitable definitive host.