Monogenea

noun plural

Mono·​ge·​nea ˌmän-ə-ˈjē-nē-ə 

: a class, subclass, or suborder of parasitic platyhelminthic worms that were formerly usually classified as trematodes but are currently considered to be more closely related to the tapeworms and that comprise flatworms ordinarily living as ectoparasites on a single usually fish host throughout the entire life cycle compare digenea