WAcanthochondria cornuta
WAcanthochondria limandae
WAncyrocephalidae
WArctic lamprey
WArgulus foliaceus
WArgulus japonicus
WCancellaria cooperii
WCeratonova shasta
WChestnut lamprey
WDiplectanidae
WEuropean river lamprey
WHenneguya zschokkei
WLepeophtheirus elegans
WLepeophtheirus pectoralis
WLernaea
WLernaeenicus sprattae
WLernaeocera branchialis
WMyxobolus cerebralis
WPacific lamprey
WPiscicola geometra
WPontobdella muricata
WSalmon louse
WSea louse
WTelosentis exiguus