About freshwater mussels

Preferred habitat
Freshwater mussels can be found in freshwater streams, rivers, billabongs, ponds, wetlands and lakes inland from the coast. They are most common in areas with muddy, silty and sandy bottoms and flowing permanent water. Their shells are relatively smooth and elliptical in shape, helping them burrow into the stream bed. Tracks can be seen along banks and sandy/muddy patches of stream bed, where mussels have moved themselves along the bottom using a muscular tongue-like appendage known as a foot. Unlike their marine and estuarine cousins, they do not attach to structures. This allows them to move with receding water levels and position themselves to the best feeding spots.

Mussels in a forest pool, an urban stream bed, and in woody debris of a forest stream

Environmental tolerances
Environmental tolerances of W. carteri are not precisely known but they can be found where water temperatures range from 4°C to over 30°C. They require adequate amount of calcium and other minerals for the formation of their shells. A few studies of a New Zealand relative of W. carteri suggest a calcium requirement of at least 1 mg/L (Forsyth, 1978, Timperley, 1987). Laboratory experiments and field collection data suggest that W. carteri is intolerant of salinities above 3.0 g/L (Klunzinger et al., unpublished data). Recent work has shown that W. carteri is intolerant to dehydration for more than a few days (Klunzinger et al. , in review).  In the summer of 2011, a large number of W. carteri died as a result of low dissolved oxygen (below 23%) and the influx of saltwater from the estuary in the Lower Canning River in the Perth area.  Livestock and urban development projects have been known to crush shells and cause severe bank erosion which have contributed to species loss.

Damage caused by cattle can be seen in the foreground of the first two images above. The third image displays an example of controlled cattle access to river - increasing stream vegetation and helping mussels avoid being trampled.

Reproduction
Precision of reproductive events in W. carteri is largely unknown. Based on current knowledge of other species, there are no distinct external features to separate males from females. Internally, mature females have specialized gill areas known as marsupia, where fertilized eggs are brooded and develop into larvae (glochidia) (e.g. McMichael and Hiscock, 1958, Humphrey, 1984, Jones et al., 1986, Walker et al., 2001). Fertilization takes place within the marsupia (Bauer and Wächtler, 2001). Once the eggs hatch, W. carteri females incubate glochidia until they are ready to be released. They then attach to fish, using a special hook or ‘larval tooth’ on both edges of their shells. Species of Unionoida use a variety of methods to attract fish, including modifying mantles or conglutinates to resemble prey that acts as lures or presenting glochidial strands as food (Strayer, 2008). The method of presenting glochidia for attachment to potential hosts of W. carteri has not been documented. On the fish, they become encysted and live as a parasite for some period of time. After they have transformed into juvenile mussels, they release themselves from their host fish and begin life in the sediments, where they grow into adults.

Hosts
The host range of W. carteri is not known with certainty but studies by Murdoch University have found that glochidia of W. carteri attach to most native freshwater fishes, but less so on feral fishes (Klunzinger et al. , unpublished data). The Freshwater Cobbler (Tandanus bostocki) is a presumed host of the species (Klunzinger et al., 2011).

Growth
The life-span of W. carteri is unknown. Other species of the Hyriidae family are estimated to live for 20 years or more. In some studies, researchers have been able to cut thin sections of the shells and examine them microscopically to confirm annual growth rings, much the same way as trees and fish have growth rings in their trunks and otoliths (ear bones), respectively.

Pristine, spring-fed freshwater mussel habitats

Click here for reference list