Other Taxonomic Groupings
Potentially Misidentified Species
A. alternata has been confused with Amathia
convoluta (Maturo), 1957.
HABITAT AND DISTRIBUTION
A. alternata occurs from Cape Hatteras south
to Florida, the Gulf of Mexico, and possibly the Caribbean.
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).
LIFE HISTORY AND POPULATION BIOLOGY
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
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).
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
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,
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
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
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Page last updated: July 25, 2001