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Species Name:    Amathia alternata
Common Name:                   (None)

 

I.  TAXONOMY

Kingdom Phylum/Division: Class: Order: Family: Genus:
Animalia Ectoprocta Gymnolaemata Ctenostomata Vesiculariidae Amathia

Growth pattern of Amathia alternata, an erect, branching bryozoan.  Drawing by J. Winston, courtesy of American Museum 
of Natural History.  Used with permission.

Species Name:
Amathia alternata Lamouroux, 1816

Common Name:
None

Species Description:
A. alternata is an arborescent bryozoan that forms upright, bushy, heavily branched colonies. Zooids are yellow to brown in color with a tubular shape measuring approximately 0.56 X 0.15 mm. Zooids are arranged in paired double rows along the stolons. Rows of zooids may either lie straight on the stolon, or twist as much as 90 around it. Zooids of successive internodes are arranged at 180 angles to each other. The lophophore bears 8 tentacles and measures 0.302 mm in diameter.


Synonymy
:
None

Other Taxonomic Groupings:
Suborder: Carnosa
Superfamily: Vesicularioidea

Potentially Misidentified Species:
A. alternata has been confused with Amathia convoluta (Maturo), 1957.


II.  HABITAT AND DISTRIBUTION 
Regional Occurrence:
A. alternata occurs from Cape Hatteras south to Florida, the Gulf of Mexico, and possibly the Caribbean.

IRL Distribution:
Within the Indian River Lagoon, A. alternata has been collected from the Sebastian Inlet area. Coastally, it has been collected at Walton Rocks and Seminole Shores. Offshore it was collected from Capron Shoals (Winston 1982, 1995).


III.  LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan:
Zooids are tubular in shape and measure 0.56 X 0.15 mm. The lophophore has 8 tentacles and measures approximately 0.302 mm in diameter. Colonies collected from the Atlantic coast of Florida, and from the IRL did not attain the larger sizes of up to 30 cm observed on the Gulf coast and described by Shier (1964 in Winston 1982).

Abundance:
A. alternata occurs year-round in Florida waters, but is most common during the winter (Winston 1982). Winston (1995) found it to be one of the most abundant winter species in the Indian River Lagoon.

Locomotion:
Sessile

Embryology:
The embryology of A. alternata is unknown.  


IV.  PHYSICAL TOLERANCES
Temperature:
A. alternata in the western Atlantic is distributed throughout warm, subtropical waters and is thus considered to be eurythermal

Salinity:
This species is generally collected in areas where salinity exceeds 30 (Winston 1982, 1995).


V.  COMMUNITY ECOLOGY
Trophic Mode:
A. alternata, like all bryozoans, is a suspension feeder. Each individual zooid in a colony has 8 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. alternata was commonly found attached to shells, beach rocks and rock overhangs. In the seagrass flats around Sebastian Inlet, it was also commonly found entangled in the Rhodophyte Solieria tenera.

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