Taxonomic name: Geukensia demissa (Dillwyn, 1817)
Synonyms: Arcuatula demissa (Dillwyn, 1817), Ischadium demissa (Dillwyn, 1817), Modiola plicatulus (Lamarck, 1819), Modiola semicostata (Conrad, 1837), Modiolus plicatulus, Mytilus demissa (Dillwyn, 1817)
Common names: Atlantic ribbed marsh mussel, ribbed horsemussel, ribbed mussel (English)
Organism type: mollusc
Geukensia demissa (ribbed mussel) is native to the east coast of North America and have been introduced to California, Mexico, Texas and Venezuela. Geukensia demissa are reported to cause problems for the California Clapper Rail (Rallus longirostris obsoletus), with whom they share the same habitat, by the trapping and drowning of birds in marshes caused by their shells sticking out of the mud.
Brachidontes exustus, Septifer bifurcatus
estuarine habitats, marine habitats
Geukensia demissa is found on the Atlantic coast of North America in intertidal zones and marshes (Cohen, 2005). It is often found living on the cordgrass Spartina foliosa. This species is abundant at the lowest shore levels of a marsh (Franz, 1997).
G. demissa is most abundant in estuarine lakes and brackish waters in Venezula (Báez et al. 2005). The highest water temperature tolerated is 56°C and salinities twice as salty as the ocean (Cohen, 2005). At low tide, G. demissa closes its shell to conserve water (Coen and Walters, undated).
Torchin et al. (2005) report on the report on the distribution, abundance, and biomass of the introduced ribbed mussel, G. demissa, at the Estero de Punta Banda (EPB), on the Pacific Coast of Baja California Norte, Mexico. The authors report it is unlikely that G. demissa competes with native bivalves for space as they occupy different habitats, however, G. demissa could be competeing with native bivalves and suspension feeders for food as thay are capable of filtering large amounts of water.
A significant impact of G. demissa was its affect on vegetation. The association between the native cordgrass (S. foliosa) and the introduced mussel was positive, increased mussel presence due to increased reproduction resulted in increased cordgrass prodcution. Increased cordgrass meant a decrease in the habitat of other benthic muddwelling invertebrates, and many of the birds that tend to forage on tidal flats (Torchin et al. 2005).
The introduced mussel has an impact on the endangered California clapper rail (see Rallus longirostris obsoletus in IUCN Red List of Threatened Species) with which it shares a common habitat. The posterior margin of the shell which protrudes above the surface of the mud can clamp on to the toes and beaks of small birds causing toe losses and sometimes death.
Geukensia demissa is a bioindicator of pollution and water quality for pollution assessment studies. This species is a filter feeder which makes it a good specimen for sediment evaluation (Coen and Walters, undated).
G. demissa improves water quality by cycling nutrients in estuarine habitats (Coen and Walters, undated). At the time of the summer tidal cycle, G. demissa can filter a volume of water that exceeds the total marsh volume (Jordan and Valiela, 1982). In Georgia, biodeposition from G. demissa is a large part of the annual marsh sediment budget which is important geologically to marshes (Smith and Frey, 1985).
On the northwest Atlantic coast this species is known as Geukensia demissa and on the northeast Pacific coast it is known as Ischadium demissum (Cohen and Carlton, 1995).
Native range: Quebec, Nova Scotia, Massachusetts, New York, Delaware, North Carolina, Connecticut, New Jersey, Florida (USA), Georgia (USA), South Carolina (WAMD, 2005; Coen and Walters, undated; Smith and Frey, 1985; Brousseau, 1984; FONS, 1998; eNature, 2005)
Known introduced range: Texas, California, Mexico, Venezuela (Báez et al. 2005; eNature, 2005; Torchin et al. 2005; NAS, 2005)
Introduction pathways to new locations
Live food trade: Carlton (1992) suggests that local dispersal pathways within the wetlands in California were most likely to be with movements of shellfish and due to ballast water introductions.
Ship ballast water: G. demissa was probably introduced into the Lake Maracaibo system, accidentally on a ships hull or in ballast water or on the legs of migratory birds (Báez et al. 2005).
Ship/boat hull fouling: G. demissa was probably introduced into the Lake Maracaibo system, accidentally on a ships hull or in ballast water or on the legs of migratory birds (Báez et al. 2005).
We have been unable to locate any management information for this particular species.
Geukensia demissa is a filter feeder that eats plankton and organic particles (Cohen, 2005) during high tide (Coen and Walters, undated). G. demissa feeds on bacterioplankton and is known as one of the few to do so. Feeding only occurs when the mussel is fully submerged (Coen and Walters, undated). During high tide though, aerial exposure reduces the filter feeding time of G. demissa (Borrero, 1987)
Geukensia demissa can live to be over 15 years (Cohen, 2005). Growth is enhanced by increasing Nitrogen levels (Evgendou and Valiela, 2002).
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Friday, 25 May 2007