Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of aquatic invertebrate animals, nearly all forming sedentary colonies. Typically about 0. 5 millimetres (1⁄64 inch) long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia. Most marine species live in tropical waters, but a few occur in oceanic trenches, and others are found in polar waters. One class lives only in freshwater environments, and a few members of a mostly marine class prefer brackish water. 5869 living species are known. One genus is solitary and the rest are colonial.

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