mon·o·ge·ne·an 
(mŏn′ə-jēnē-ən)
(mŏn′ə-jēnē-ən)n.
Any of various flatworms of the class Monogenea that typically pass the entire life cycle as an ectoparasite on an individual fish.
[From New Latin Monogenea, class name (originally an order name) : MONO- + Greek geneā, race; see GENEALOGY.]
mon′o·gene·an adj.