Free-living larval form in the life cycle of flukes.

The first developmental stage larva of a fluke which hatches from the egg and penetrates the intermediate host.

A miracidium is a small free-living larval stage of parasitic flatworms in the class Trematoda. It is released from eggs which are usually shed in the faeces of its vertebrate host. When an egg is immersed in water, its operculum liberates the miracidium, which swims using cilia to find the first host in its life cycle, a mollusc.