Alasmidonta undulata 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Bivalvia Unionoida Unionidae

Scientific Name: Alasmidonta undulata Say, 1817
Common Name(s):
English Triangle Floater
Taxonomic Notes: Taxonomic confusion surrounds two morphologically similar species: Alasmidonta undulata and Alasmidonta triangulata. Historically, specimens assigned to A. undulata were identified as A. triangulata. Graf and Cummings (2007) classify them as separate species and A. undulata is considered the sister species to Alasmidonta arcula (Bogan et al. 2008).

A list of synonyms for this species can be found on The MUSSEL project web site (Graf and Cummings 2011).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2011
Date Assessed: 2011-07-22
Assessor(s): Cordeiro, J.
Reviewer(s): Böhm, M. & Collen, B.
Contributor(s): Dyer, E., Soulsby, A.-M., Whitton, F., McGuinness, S., De Silva, R., Milligan, H.T., Kasthala, G., Thorley, J., Herdson, R., McMillan, K. & Collins, A.
Alasmidonta undulata has been assessed as Least Concern because it has a large distribution, can withstand higher levels of habitat degradation than similar species, utilises many different fish hosts, and is not being impacted by any major threat process across its wide range. However, localised declines have been observed in the southern part of its range, and the reasons for these declines warrant further investigation.

Geographic Range [top]

Range Description:In the United States, this species occurs in Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, South Carolina, Vermont and Virginia. NatureServe (2009) have classified it as Critically Imperilled in Florida, Georgia, Maryland, West Virginia, and it is Possibly Extirpated in Delaware and District of Columbia.

In Canada, this species occurs in New Brunswick, Nova Scotia, Ontario and Quebec.

The range of this species extends from the lower St. Lawrence River Basin south to the Ogeechee River Basin in Georgia (Bogan and Alderman 2008, Bogan et al. 2008).
Countries occurrence:
Canada (New Brunswick, Nova Scotia, Ontario, Québec); United States (Connecticut, Delaware - Possibly Extinct, District of Columbia - Possibly Extinct, Florida, Georgia, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, South Carolina, Vermont, Virginia, West Virginia)
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species is wide ranging across the Atlantic Slope, and maintains some fairly stable populations. Although widespread and even common in some areas, the species has experienced pockets of decline in the southern portion of its range for unknown reasons. This includes declines in the populations of North Carolina, South Carolina, Virginia, Georgia, and also central New York. More populations exist in New England than anywhere else throughout its known range along the Atlantic coast (NatureServe 2009).
Current Population Trend:Stable
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:Northern populations of this species avoid larger rivers, preferring small streams going far up towards the headwaters. This species favours a steady flow of water rather than riffles or rough water. Occasionally, it can be found in lakes, ponds and canals. It lives mostly in a mixture of coarser or finer gravel with sand and mud, or in between large stones (Clarke 1981). Southern populations are also found in big rivers in muddy sand with moderate current (Heard 1979).

Hostfish include the Blacknose Dace (Rhinichthys atratulus), Common Shiner (Luxilus cornutus), Fallfish (Semotilus corporalis), Largemouth Bass (Micropterus salmoides), Longnose Dace (Rhinichthys cataractae), Pumpkinseed (Lepomis gibbosus), Slimy Sculpin (Cottus cognatus) and White Sucker (Catostomus commersoni), (Watters et al. 1999 from Nedeau et al. 2000).

Threats [top]

Major Threat(s): It is unlikely that any major threat is impacting this species. It seems to be less affected by habitat degradation than other mussel species, and it is thought to use a greater diversity of fish hosts than most other mussels found in similar ecosystems (Nedeau et al. 2000, Nedeau et al. 2003). However, some localised declines have been observed and the reasons for this need to be identified in order to avoid similar declines elsewhere.

Conservation Actions [top]

Conservation Actions: This species has been given a NatureServe Global Heritage Status Rank of G4 - apparently secure (NatureServe 2009), and was assigned an American Fisheries Society Status of Special Concern (1 Jan 1993). In South Carolina, this species is listed as State Endangered (Bogan and Alderman 2008).

There are no species-specific conservation measures in place for this species, however in places its distribution coincides with protected areas. Further research is recommended into the causes of decline in the southern portions of this species' range.

Citation: Cordeiro, J. 2011. Alasmidonta undulata. The IUCN Red List of Threatened Species 2011: e.T189106A8683096. . Downloaded on 24 June 2018.
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