epizooen
Ep`i*zo"ön, n.; pl. Epizoa. Etym: [NL., fr. Gr. (Zoöl.) Defn: One of the artificial group of invertebrates of various kinds, which live parasitically upon the exterior of other animals; an ectozoön. Among them are the lice, ticks, many acari, the lerneans, or fish lice, and other crustaceans.