II. HABITAT AND
DISTRIBUTION
Regional Occurrence:
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.
IRL Distribution:
A. truncata has
been collected from the Sebastian Inlet area during November. It is likely to
occur throughout the Indian River Lagoon.
III. LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan:
Tubular portion measures approximately 0.70 X
0.06 mm.
Abundance:
In the IRL, it is considered a common fouling
organism (Winston 1995).
Locomotion:
Sessile
Reproduction:
A. truncata has
been collected from the IRL during November, but was not reproductive at the
time of collection (Winston 1982).
Embryology:
When reproductive, embryos of A. truncata
are brooded in membranous ovisacs.
IV. PHYSICAL TOLERANCES
Temperature:
With its nearly world-wide distribution, A.
truncata is able to withstand fluctuations in water temperature and is thus
considered to be eurythermal.
Salinity:
A. truncata was typically collected from waters
where salinity remained above
30 ‰.
V. COMMUNITY ECOLOGY
Trophic Mode:
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.
Habitats:
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.
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. In the IRL, A. truncata was found in association with hydrozoans,
specifically Thyroscyphus ramosus.
VI. SPECIAL STATUS
Special Status:
None.
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.
Economic Importance:
None.
Report by: K. Hill,
Smithsonian Marine Station
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Page last updated: July 25, 2001
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