Other Taxonomic Groupings
American Museum of Natural History # 575
A. truncata colonies consist of creeping stolons from which straight tubular portions
arise. The tubular portions are divided into basal areas that resemble
stalks, and terminal regions with opercula at the frontal surface. Polypides
span both the basal and tubular portions. Stolon and tubular regions are
studded with tiny tubercles, but no annulations. Tubular portion measures
approximately 0.70 X 0.06 mm (Winston 1982).
HABITAT AND DISTRIBUTION
With the exception of polar seas, A. truncata has a world-wide distribution. In the Western Atlantic it is most common from Cape Hatteras south through Florida and the Gulf of Mexico to the Caribbean and Brazil.
A. truncata has been collected from the Sebastian Inlet area during November. It is likely tooccur throughout the Indian River Lagoon.
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
Tubular portion measures approximately 0.70 X 0.06 mm.
In the IRL, it is considered a common fouling organism (Winston 1995).
A. truncata has been collected from the IRL during November, but was not reproductive at the time of collection (Winston 1982).
When reproductive, embryos of A. truncata are brooded in membranous ovisacs.
With its nearly world-wide distribution, A. truncata is able to withstand fluctuations in water temperature and is thus considered to be eurythermal.
A. truncata was typically collected from waters where salinity remained above 30‰.
A. truncata, like all bryozoans, is a suspension feeder. Each individual zooid in a colony has 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. truncata was collected in the Sebastian Inlet area from the stems of the hydrozoan Thyroscyphus ramosus.
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. In the IRL, A. truncata was found in association with hydrozoans, specifically Thyroscyphus ramosus.
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.
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
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Page last updated: July 25, 2001