Kingdom Animalia Class Trematoda Family Accacoeliidae Rank Species | Phylum Platyhelminthes Order Plagiorchiida Genus Accacoelium | |
Similar Molidae, Monogenea, Sunfish, Digenea, Tetraodontiformes | ||
Accacoelium contortum is a parasitic flatworm of the class Trematoda. It lives in the gills and oral cavity of the ocean sunfish, Mola mola, and was first described by Swedish-born naturalist Karl Rudolphi in 1819.
Accacoelium contortum is one of the most common sunfish parasites and has been reported in the Mediterranean Sea, the Northeast Atlantic Ocean and the South Pacific. In a study in Spain, 47.2% of 106 sunfish examined were found to host Accacoelium contortum.
Most trematodes are internal parasites, but Accacoelium contortum is also found on the outside of its host. It lacks the hooks and clamps found on other external parasites, and instead attaches using a ventral sucker. It is found in clusters in the mouth, gills and pharynx, but can also survive in the gastrointestinal tract.
Accacoelium contortum induces a strong immune response in its host, leading to inflammation, hyperplasia and necrosis at the site of attachment. In some cases, the parasites can end up encased in host tissue.