Marine Phyla Pages -- Coastal Carolina University 

Bryozoa

Lophophorata

   Bryozoa

   Brachiopoda

   Phoronida

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Main

Defining Characteristics

Bryozoans, or "moss animals," are aquatic organisms, living for the most part in colonies of interconnected individuals. A few to many millions of these individuals may form one colony.  Colonies may be mistaken for hydroids, corals, or even seaweeds.

Systematics

The mouth opens into a U-shaped gut; the anus is located just outside the lophophore. The body also contains a coelom and gonads; there is a small central ganglion, or "brain," but no specialized excretory or respiratory systems. Zooids are usually connected to each other by thin strands of tissue.  In most bryozoans, several different types of zooids coexist in a colony, each one specialized for a particular function. Feeding zooids are known as autozooids, whereas specialized nonfeeding zooids may be called heterozooids. Heterozooids are dependent on functioning autozooids for nutrients. Heterozooids include forms specialized for producing and brooding eggs, or, more rarely, sperm. Avicularia are small heterozooids in which the zooecium and operculum form a beak-like, snapping structure that deters small predators. Vibracula bear long setae, or bristles, and are thought to function in cleaning the bryozoan colony, while kenozooids are small heterozooids that strengthen and support the colony as well as fill space. In conclusion, bryozoan colonies show a range of integration. The most integrated colonies behave like individual organisms, for the zooids making up the colony are all specialized for certain functions and connected to each other.

Habitat

Some bryozoans encrust rocky surfaces, shells, or algae. Others form lacy or fan-like colonies that in some regions may form an abundant component of limestone. Bryozoan colonies range from millimeters to meters in size, but the individuals that make up the colonies are rarely larger than a millimeter.

Bryozoans may also foul pilings, piers, and docks. Certain freshwater species occasionally form great jellylike colonies so huge they clog public or industrial water intakes.

Feeding

Bryozoans feed on small microorganisms, including diatoms and other unicellular algae. These are trapped by the protrusible ciliated feeding tentacles, or lophophore.

Other Information

Despite the fact that there are about 5000 living species, with several times that number of fossil species, the Bryozoa remain largely unknown to most people.

Bryozoans produce a remarkable variety of chemical compounds, some of which may find uses in medicine.

Bryozoans are preyed on by grazing organisms such as sea urchins and fish, and are also subject to competition and overgrowth from sponges, algae, and tunicates.

Bryozoa Links

http://www.ucmp.berkeley.edu/bryozoa/bryozoa.html