Dwarf wedgemussel
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| Alasmidonta heterodon I. Lea, 1830 |
The Dwarf wedgemussel (Alasmidonta heterodon) is an endangered species of freshwater mussel. It is a rare species confined to rivers and waterways along the Atlantic coast of North America, from North Carolina to New Brunswick. It is the only freshwater mussel from North America that has two lateral teeth on the right valve and only one on the left side.
The Dwarf wedgemussel is a small mussel, whose shell size rarely exceeds 45 mm in length and 25 mm high. The trapezoidal-shaped shells are colored brown or yellowish-olive, with reddish brown or greenish rays in young or pale specimens. The nacre is bluish or silvery white, and is iridescent on the posterior.
Details of reproduction are slim, but it is believed to be not unlike that of other mussels. It spawns in late summer.
It lives in muddy sand, cobble, firm silt and gravel bottoms of creeks and rivers in areas of slow to moderate current and little silt deposit. At times, it has also been found to utilize the root systems of trees at the water's edge. It is believed to be primarily sessile, with limited movement in the substrate (meaning it generally stays attached at one spot).
There are only 20 known remaining populations, and these continue to be endangered to agricultural and industrial runoff. Road and dam construction, as well as channelization and removal of shoreline vegetation, are also threats. It is currently on the U.S. Endangered Species List, classified as endangered since March 1990. It is also classified as endangered in the states of Connecticut, Massachusetts, Maryland, North Carolina, New Hampshire, New Jersey, New York, Pennsylvania, Virginia, and Vermont. The only recorded Canadian location for the Dwarf wedgemussel is the Petitcodiac River of New Brunswick. A specimen was last collected there in 1960, at which time the species was classified as being common. It became extirpated in 1968, following construction of a causeway.
[edit] References
- Bogan (2000). Alasmidonta heterodon. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes a brief justification of why this species is endangered and the criteria used.
- Dwarf Wedgemussel Recovery Plan: US Fish and Wildlife Service (PDF document)
- NatureServe Explorer report
- Dwarf Wedgemussel Fact Sheet
