Monogenea are small parasitic flatworms. The body is usually flat and oval, and rarely longer than about 2cm. Like other flatworms, Monogenea have no coelom. They have a simple digestive system consisting of a mouth opening with a muscular pharynx and an intestine with no anus. Monogeneans have a collection of various attachment structures. The anterior structures are collectively termed the prohaptor, while the posterior ones are collectively termed the opisthaptor.
Photo Credit: From the English Wikipedia: PD A monogenean parasite of fishes. Released into the public domain by [http://www.fishdisease.net FishDisease.net].