Aquatic invertebrate of the phylum Bryozoa ("moss animals"), members (called zooids) of which form colonies.
Each zooid is a complete and fully organized animal. Species range in size from a one-zooid "colony" small enough (less than 0.04 in., or 1 mm, long) to live between sand particles to colonies that hang in clumps or chains as much as a 1.6 ft (0.5 m) across. The texture of colonies varies from soft and gelatinous to hard with calcium-containing skeletons. Freshwater bryozoans attach primarily to leaves, stems, and tree roots in shallow water. Marine bryozoans have a wide range of habitats, from coastal areas to great ocean depths, but are most common just below the tidemarks. Bryozoans feed by capturing plankton with their tentacles.