Aquatic Species at Risk - Salamander Mussel

Salamander Mussel

Salamander Mussel
Photo credit:
Todd Morris, DFO

SARA Status: Endangered
COSEWIC Status: Endangered

Region: Ontario

Region: Ontario

Did You Know?

Freshwater mussels are molluscs, soft-bodied animals without a skeleton (invertebrates), that live on the bottom of streams, rivers, lakes and ponds. They use a muscular foot to burrow and crawl and have a pair of hinged shells. Mussels are filter feeders — nature’s water purifiers — and are food for other wildlife like fishes, otters, mink, muskrats and some birds. They are also among the most endangered creatures in the world.

Related Information

COSEWIC Assessment and Status Report on the Mudpuppy Mussel Simpsonaias ambigua in Canada (2011)

Recovery Strategy for Northern Riffleshell (Epioblasma torulosa rangiana), Snuffbox (Epioblasma triquetra), Round Pigtoe (Pleurobema sintoxia), Mudpuppy Mussel (Simpsonaias ambigua) and Rayed Bean (Villosa fabalis) in Canada. (2007)


The Salamander Mussel (Simpsonaias ambigua), also known as the Mudpuppy Mussel, is one of Canada’s 54 freshwater mussel species and is the only living member of the genus Simpsonaias. It is also the only freshwater mussel that uses a non-fish host. As the name suggests, this small mussel uses a salamander - the Mudpuppy (Necturus maculosus) - as its host. It has the following characteristics:

  • shell is thin, fragile, oval-to-elliptical in shape, and considerably elongated;
  • thicker at the front end than the back end;
  • shell is rounded at both ends, while top and bottom edges are nearly parallel;
  • the raised part at the top of the shell (beak) is slightly swollen and sculptured with four-to-five double-looped ridges;
  • maximum shell length is about five cm;
  • outside of shell is yellowish-tan to dark brown with no markings;
  • inside of shell (nacre) is bluish-white, shiny on the back half and sometimes tinged with pink; and
  • triangular teeth at the front edge of the hinge are small, low and rounded - one in each half of the shell.
Mudpuppy mussel

Simpsonaias ambigua
Photo credit: Environment Canada


Salamander Mussel distribution as described in the following paragraphs

Map showing the Salamander Mussel distribution in Canada. The map indicates areas of current and historic sites in southern Ontario.

In Canada, the Salamander Mussel was historically found in the Detroit, Sydenham and Thames rivers in Ontario. It is now restricted to a 50 km reach of the East Sydenham River, where it appears to be reproducing. This mussel, historically also found in 14 American states, has been lost from 60 per cent of formerly occupied rivers and streams in the United States.

The Salamander Mussel is most often found burrowed in sand or silt under large, flat rocks in shallow areas with swift currents, although it can also be found in mud or on gravel bars. Habitat is dependent on areas that meet nesting and sheltering requirements of its larval host, the Mudpuppy salamander. Here, the glochidia (the mussel’s larvae) are released and infest the gills of the Mudpuppy. When the glochidia have transformed into juvenile mussels, they are likely released into the hiding place of the Mudpuppy, creating large clusters of these mussels in one area. It is believed that spawning occurs in late summer and the glochidia are released the following spring or summer. Adults are essentially sessile, and may move only a few metres through the substrate.

Like all species of freshwater mussels, the Salamander Mussel filters its food from the water. Bacteria and algae are its primary food sources.


Declining habitat quality from intense agriculture, urban development and pollution continue to threaten this mussel. The continued existence of this species in Canada may also depend on the status of its salamander host, the Mudpuppy, which is intolerant of siltation and could be threatened by increasing sediment loads from agricultural activities in the Sydenham River watershed. It is also believed that this mussel was lost from the Detroit River, due to the impact of the invasive Zebra Mussel (Dreissena polymorpha). This species is difficult to find and may be under-surveyed.

Further Information

Under SARA, a recovery strategy and an action plan have been developed to prevent the loss of the Salamander Mussel in Canada and to return healthy self-sustaining populations of this species to the Sydenham and Thames rivers and the St. Clair River delta.

Research, land and water stewardship, monitoring and awareness activities are underway. Provincial legislation regulating agricultural nutrients and protecting clean water in Ontario have been enacted. Critical habitat for the Salamander Mussel has also now been identified under SARA, allowing for greater protection and recovery of its habitat.

Text Sources: COSEWIC Status Report on Mudpuppy Mussel (Simpsonaias ambigua), 2001; Metcalfe-Smith et al. Photo Field Guide to the Freshwater Mussels of Ontario, 2005; Fisheries and Oceans Canada. Action Plan for the Sydenham River in Canada [proposed], 2012; Fisheries and Oceans Canada. Recovery Strategy for Northern Riffleshell, Snuffbox, Round Pigtoe, Mudpuppy Mussel and Rayed Bean in Canada [proposed], 2012.

For more information, visit the SARA Registry.

Scientific Information

Scientific Name:  Simpsonaias ambigua
SARA Status: Endangered (June 2003)
COSEWIC Status: Endangered (May 2001; May 2011)