Microcotyle is a genus which belongs to the phylum Platyhelminthes and class Monogenea. Species of Microcotyle are ectoparasites that affect their host by attaching themselves as larvae on the gills of the fish and grow into adult stage. This larval stage is called oncomiracidium, and is characterized as free swimming and ciliated. Although not really known to cause that much damage in marine wildlife, some of them are reported to cause agricultural problems like Microcotyle sebastis as an example. Microcotyle sebastis commonly affects Sebastes schlegeli, a maricultured fish in Korea.