Species Description:
T. floridana is an encrusting species
whose colonies sometimes rise into erect rosettes or frills (Winston 1982).
Colonies are gray to white in color, with individual zooids quadrangular in
shape and of variable size. Typical zooid size is 0.45 - 0.50 mm in height, and
0.20 - 0.25 mm in width. Distinct grooves separate individuals. The frontal
membrane covering the colony surface is lightly calcified but perforated, except
at the distal opesia and 2 large opesiules proximal to it (Winston 1982). One of
the opesiules is generally larger than the other, and is bounded by a descending
tubular portion of the cryptocyst continuing to the basal wall of the zooid
(Winston 1982). The opesia themselves are hoof-shaped. Avicularia between zooids
are arch-shaped, with the point of the mandible bent. Spicules occur in the body
cavity and resemble calipers. Polypides collected in the winter months had
large, bulbous intertentacular organs (Winston 1982).
Synonymy:
None
Other Taxonomic Groupings:
Suborder: Anasca
Potentially Misidentified Species:
Osburn (1940) first described
T. floridana as a subspecies of T.
gothica. However, T. gothica had originally been described from the
Pacific Ocean around Mexico. T. gothica specimens from the Pacific have
large ovicells that may brood several embryos at once. They also have spicules
in the shape of open compasses, and wider opesiae with no adoral tubercles (Winston
1982). Conversely, Atlantic coast specimens of T. floridana have not been
described with ovicells; their spicules are caliper shaped, and they possess
adoral tubercles.
II. HABITAT AND
DISTRIBUTION
Regional Occurrence:
T. floridana occurs from Cape Hatteras south to Florida, the Gulf of
Mexico and the Caribbean.
IRL Distribution:
T. floridana occurs year-round at coastal locations and within the IRL
(Winston 1982).
III. LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan:
Zooids are variable in size and range from 0.45 - 0.50 mm in height, 0.20 -
0.25 mm in width.
Abundance:
T. floridana can be collected year-round in
Florida, but is most abundant in the winter months. It was reported by Winston
to be the most abundant bryozoan encrusting stems of the hydroid Thyroscuphus
ramosus in winter. Colonies are least abundant in the summer.
Locomotion:
Sessile
Reproduction:
No ovicells are present in T. floridana.
IV. PHYSICAL TOLERANCES
Temperature:
As a species which occurs year-round, and in
greater abundance throughout the winter months, T. floridana is considered to be eurythermal.
Salinity:
T. floridana is typically collected from
areas where salinity exceeds 30 ‰ (Winston 1982).
V. COMMUNITY ECOLOGY
Trophic Mode:
T. floridana, like all bryozoans, is a
suspension feeder. Each individual zooid in a colony has ciliated tentacles that
are extended to filter phytoplankton less than 0.05 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 could clear 8.8 ml of water per day.
Habitats:
Typical habitat for ectoprocts in the Indian River
Lagoon include seagrasses, drift algae, oyster reef, docks, pilings,
breakwaters, and man-made debris (Winston 1995). T. floridana is the most
abundant species on the stems of the hydroid Thyroscyphus ramosus during
the winter. It was also found encrusting rhodophytes at coastal
locations and attached to breakwater rocks at Sebastian Inlet, where it forms
large masses in January (Winston 1982).
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 supporting substrata: mangrove roots, oyster beds, mussels,
etc.
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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irl_webmaster@si.edu
Page last updated: July 25, 2001
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