Zooid

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A zooid or zoöid /ˈz.ɔɪd/ is a single animal that is part of a colonial animal. The zooids can either be directly connected by tissue (e.g. corals, Catenulida, Siphonophorae, Pyrosome or Ectoprocta) or share a common exoskeleton (e.g. Bryozoa or Pterobranchia). The colonial organism as a whole is called a zoon /ˈz.ɒn/, plural zoa (from greek zòon ζώον meaning animal; plural zòa, ζώα).

The term zooid has historically also been used for an organic cell or organized body that has independent movement within a living organism, especially a motile gamete such as a spermatozoon (in the case of algae now zoid), or an independent animal-like organism produced asexually, as by budding or fission.