Zooids are vase-shaped or subcylindrical. Individual functional zooids measure
approximately 0.38 X 0.17 mm, while degenerated zooids measure 0.38 X 0.19 mm.
Zooids and stolons of living colonies are studded with small, star-shaped black
pigments. The polypide and lophophore are not pigmented. The lophophore measures
approximately 0.246 in diameter, and bears 10 tentacles. Both the body wall and
the lophophore are somewhat flexible to enhance scanning while feeding.
Other Taxonomic Groupings:
Potentially Misidentified Species:
B. imbricata in
the Indian River Lagoon could be confused with B. pustulosa, a related
bryozoan. In overall morphology, zooid clusters of B. imbricata
have largely been described as non-helical; however, in IRL specimens, zooids of
this species did form a partial helix around the stolon (Winston 1982). They
thus resemble the overall morphology of B. pustulosa. These species can
be differentiated base on the number of tentacles present: B. imbricata
has 10 tentacles, while B. pustulosa has 8 tentacles.
II. HABITAT AND
In the western Atlantic, B. imbricata has
been reported from cool water areas north of Florida; however, it is also known
from warm water areas in the Mediterranean and the Red Sea.
has been collected from the IRL at the Sebastian Inlet grass flats, and
coastally at the Ft. Pierce breakwater. It is likely to have a wider
distribution within the lagoon, but as yet, no documentation exists.
III. LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan:
Functional zooids measure approximately 0.38 X 0.17
mm. Degenerated zooids measure 0.38 X 0.19 mm. Stolon diameter is approximately
0.23 mm in diameter. Lophophore diameter averages 0.246 mm.
was collected from March to September in the IRL. Little information on its
The embryology of B. imbricata is unknown.
IV. PHYSICAL TOLERANCES
B. imbricata is
a eurythermal species known from both temperate and sub-tropical waters.
V. COMMUNITY ECOLOGY
like all bryozoans, is a suspension feeder. Each individual zooid in a colony
has 10 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.
Both the polypide and the body wall of B. imbricata
are highly flexible. With the polypide retracted, the zooid is compressed
against the substratum; with the polypide expanded, the zooid elongates and
rises to a vertical or diagonal position with respect to the substratum. B.
imbricata holds its tentacles straight while feeding. The polypides slowly
scan the water column in a circular motion in search of appropriately sized
particulates. Adjacent lophophores in this species are well separated. Polypides
of neighboring zooids may occasionally touch each other while scanning, but they
will quickly withdraw.
Typical habitat for ectoprocts in the Indian River
Lagoon include seagrasses, drift algae, oyster reef, dock, pilings, breakwaters,
and man-made debris (Winston 1995).
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. At Sebastian Inlet, B. imbricata is commonly found in association with
algae, especially Solieria tenera, a common Rhodophyte. However, at other
IRL and coastal locations, B. imbricata is found attached to the
undersides of rocks and ledges, and in holes in worm-reef (Phragmatopoma
spp.) mounds (Winston 1982).
VI. SPECIAL STATUS
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
Report by: K. Hill,
Smithsonian Marine Station
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Page last updated: July 25, 2001