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The difinitive hosts are fish eating mammals. The eggs are released into the biliary passages of the host and leave the body in the feces. Unlike other trematodes the eggs does not hatch until it is ingested by a suitable snail. The miracicium fully formed at the time of release then hatches in the snail, metamorphoses from a sporocyst, rediae and finally a cercariae. Once the cercariae has left the snail it must find a suitable fish within a very short time or it will die. Once a fish is found the cercariae burrow beneath the scales, encysting as a metacercaria on muscle tissue. Once this metacercaria is ingested by man the larva are released and migrate to the bile duct and from there to the distal biliary capillaries where it matures.