Species Description:
M. savartii
forms encrusting colonies that may be one or more layers thick. Zooid shape
varies from elongate to rectangular or quadrangular. Individuals measure
an average of 0.27 X 0.55 mm. A variable denticulated (toothed) shelf is formed
under the proximal half of the frontal surface. Proximal teeth are variable in
number or absent. Zooid walls are heavily calcified and have fine tubercles. No
avicularia are present.
Synonymy:
None
Other Taxonomic Groupings:
Suborder: Anasca
II. HABITAT AND
DISTRIBUTION
Regional Occurrence:
M. savartii is
highly cosmopolitan in warm water areas. In the western Atlantic, it ranges from
the Carolinas to Brazil, including Florida, the Gulf of Mexico and the
Caribbean.
IRL Distribution:
M. savartii was
collected from the Sebastian Inlet area, both at the inlet, and in the adjacent
grass flat areas (Winston 1982). It was also collected from coastal stations at
Walton Rocks, Seminole Shores, and on Capron Shoals.
III. LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan:
Individual zooids measure an average of 0.27 X 0.55
mm.
Abundance:
M. savartii
occurs year round, but is most abundant in April and October. In the IRL, it is
considered a fouling organism (Winston 1995).
Locomotion:
Sessile
Reproduction:
No ovicells are present in this species.
Like other membraniporids, Membranipora savartii spawns small eggs which
develop into planktonic cyphonautes larvae.
IV. PHYSICAL TOLERANCES
Temperature:
As it is present year-round, M. savartii is
considered to be eurythermal.
Salinity:
M. savartii was
typically collected in areas where salinity exceeded 30 ‰ (Winston 1995).
V. COMMUNITY ECOLOGY
Trophic Mode:
M. savartii,
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 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). M. savartii was typically found on
dead shells and rock substrata at all locations (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 support structures: 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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Page last updated: July 25, 2001
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