|Listed||June 20, 1991|
|Family||Unionidae (Freshwater Mussel)|
|Description||Similar to the common mapleleaf, but with a more inflated shell.|
|Habitat||Riffle areas of large clearwater streams.|
|Reproduction||Female stores sperm in gills; glochidia are released into the stream after hatching.|
|Threats||Low numbers, reproductive failure.|
|Range||Kentucky, Minnesota, Tennessee, Wisconsin|
The winged mapleleaf (Quadrula fragosa ) is a freshwater mussel closely related to the mapleleaf, a common mussel species in eastern North America. It can be distinguished by its more inflated shell, which is more quadrate in outline, and the beaks on the shell, which are turned forward and more elevated.
See the Upland Combshell (Epioblasma metastriata ) entry.
This species occupies gravel bars in the shallow, clear waters of large rivers.
The winged mapleleaf has been found in four river systems in eleven states: the Mississippi, Tennessee, Ohio, and Cumberland systems in Ohio, Indiana, Missouri, Tennessee, Kansas, Nebraska, Iowa, Illinois, Wisconsin, Oklahoma, and Kentucky. Collections of the winged mapleleaf were not unusual until about 1920, after which they became rare and many experts considered the species extinct.
At the dawn of the twenty-first century, a single, small population of the winged mapleleaf survived in the St. Croix River along the border of Minnesota and Wisconsin. This population was restricted to less than 5 mi (8 km) of river within a national scenic riverway administered by the National Park Service.
The population density at this one remaining site was one individual per 560 sq ft (52 sq m), constituting less than 0.02% of the mussel community. This community consists of 32 species of mussels, including rare species such as the federally endangered Higgins' eye (Lampsilis higginsi ) and the spectacle case (Cumberlandia monodonta ) and salamander mussel (Simpsonaias ambigua ), which are candidates for federal listing.
The preferred habitat of the winged mapleleaf— riffles or gravel bars in large clearwater streams— has been largely eliminated by impoundment, channelization, and sedimentation.
Conservation and Recovery
The sole surviving population is at extreme risk because of an apparent reproductive failure. During surveys in 1988 and 1989 researchers failed to find any individuals less than four years old or to find females carrying eggs. Related species that were collected during the survey included individuals of all age classes. If this population is truly failing to reproduce, its extinction is certain.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
Doolittle, Thomas C. J. 1988. "Distribution and Relative Abundance of Freshwater Mussels in the Saint Croix National Scenic Riverway." Cable Natural History Museum, Sigurd Olson Environmental Institute, Ashland, Wisconsin.
Havlik, M. E., and L. L. Marking. 1980. "A Quantitative Analysis of Naiad Mollusks from the Prairie du Chien, Wisconsin, Wisconsin Dredge Material Site on the Mississippi River." Bulletin of the American Malacological Union 1977: 9-12.