Bryozoan, << `bry` uh ZOH uhn, >> is a type of water animal that lives only in colonies. Bryozoans are invertebrates (animals without backbones). There are approximately 5,000 species of bryozoans. They are found throughout the world in many water habitats, from shallow ponds to the deepest oceans. Colonies of freshwater bryozoans may form large, jellylike masses, or they may form delicate, branchlike networks on water plants. Marine bryozoan colonies may resemble seaweed. They also may form lacy, hard-shelled or mosslike crusts or mounds on rocks, pilings, or other solid surfaces. Bryozoans are also called moss animals.
A bryozoan colony consists of microscopic, connected individuals called zooids. Each bryozoan zooid has a boxlike or tube-shaped body that contains fluid and a U-shaped gut. A cluster of tentacles called a lophophore extends into the water to trap small particles of food. Bryozoan fossils date from 500 million years ago.
