Smithsonian Marine Station at Fort Pierce

Website Search Box

Advanced Search

Growth pattern of Amathia alternata, an erect, branching bryozoan. Drawing by J. Winston, courtesy of American Museum of Natural History. Used with permission.

Species Name: Amathia alternata Lamouroux, 1816
Common Name: None
Synonymy: None

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Animalia Ectoprocta Gymnolaemata Ctenostomata Vesiculariidae Amathia

    Other Taxonomic Groupings

    Suborder: Carnosa
    Superfamily: Vesicularioidea

    Potentially Misidentified Species

    A. alternata has been confused with Amathia convoluta (Maturo), 1957.


    Regional Occurrence

    A. alternata occurs from Cape Hatteras south to Florida, the Gulf of Mexico, and possibly the Caribbean.

    IRL Distribution

    Within the Indian River Lagoon, A. alternata has been collected from the Sebastian Inlet area. Coastally, it has been collected at Walton Rocks and Seminole Shores. Offshore it was collected from Capron Shoals (Winston 1982, 1995).


    Age, Size, Lifespan

    Zooids are tubular in shape and measure 0.56 X 0.15 mm. The lophophore has 8 tentacles and measures approximately 0.302 mm in diameter. Colonies collected from the Atlantic coast of Florida, and from the IRL did not attain the larger sizes of up to 30 cm observed on the Gulf coast and described by Shier (1964 in Winston 1982).


    A. alternata occurs year-round in Florida waters, but is most common during the winter (Winston 1982). Winston (1995) found it to be one of the most abundant winter species in the Indian River Lagoon.




    The embryology of A. alternata is unknown.



    A. alternata in the western Atlantic is distributed throughout warm, subtropical waters and is thus considered to be eurythermal


    This species is generally collected in areas where salinity exceeds 30 ‰ (Winston 1982, 1995).


    Trophic Mode

    A. alternata, like all bryozoans, is a suspension feeder. Each individual zooid in a colony has 8 ciliated tentacles that are extended to filter phytoplankton less than 0.045 mm in size (about 1/1800 of an inch) from the water column. Bullivant (1967; 1968) showed that the average individual zooid in a colony can clear 8.8 ml of water per day.


    Typical habitat for ectoprocts in the Indian River Lagoon include seagrasses, drift algae, oyster reef, dock, pilings, breakwaters, and man-made debris (Winston 1995). A. alternata was commonly found attached to shells, beach rocks and rock overhangs. In the seagrass flats around Sebastian Inlet, it was also commonly found entangled in the Rhodophyte Solieria tenera.

    Associated Species

    Seagrasses as well as floating macroalgae, provide support for bryozoan colonies. In turn, bryozoans provide habitat for many species of juvenile fishes and their invertebrate prey such as polychaete worms, amphipods and copepods (Winston 1995). Bryozoans are also found in association with other species that act as support structures: mangrove roots, oyster beds, mussels, etc.


    Benefit in IRL

    Bryozoans are ecologically important in the Indian River Lagoon due to their feeding method. As suspension feeders, they act as living filters in the marine environment. For example, Winston (1995) reported that bryozoan colonies located in 1 square meter of seagrass bed could potentially filter and recirculate an average of 48,000 gallons of seawater per day.


    Maturo FJS. 1957. A study of the Bryozoa of Beaufort, North Carolina, and vicinity. J Elisha Mitchell Sci Soc 73: 11-68.

    Shier DE. 1964. Marine bryozoa from northwest Florida. Bull Mar Sci 14: 603-662.

    Winston JE. 1982. Marine bryozoans (Ectoprocta) of the Indian River area (Florida). Bull Amer Mus Nat Hist 173: 99-176.

    Winston JE. 1995. Ectoproct diversity of the Indian River coastal lagoon. Bull Mar Sci 57: 84-93.

Report by: K. Hill, Smithsonian Marine Station
Submit additional information, photos or comments to:
Page last updated: July 25, 2001

[ TOP ]