any member of the phylum Entoprocta, a group of aquatic invertebrate animals, composed of more than 100 species. Entoprocts occur throughout the world, primarily in marine habitats, although one genus, Urnatella, is a freshwater form. Entoprocts may either exist singly or form colonies of communicating members, called zooids, by budding. The zooids measure only about 0.4 to 5 mm (0.016 to 0.2 inch) in height. Each of them has a stalk (peduncle), which may be jointed, that attaches to shells, seaweed, or to other animals, such as sponges, bryozoans, hydroids, and segmented worms, that produce water currents
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