U.S. Fish & Wildlife Service

What is the winged

mapleleaf?

Endangered Species Facts

The winged mapleleaf is

found only in the St. Croix

along the Wisconsin and

Minnesota border.

The winged mapleleaf mussel is an endangered species. Endangeredspecies are animals and plants that are in danger of becoming extinct.

Threatened species are animals and plants that are likely to become

endangered in the foreseeable future. Identifying, protecting and restoring

endangered and threatened species is the primary objective of the U.S.

Fish and Wildlife Service’s endangered species program.

Scientific Name - Quadrula fragosa

Appearance - Winged mapleleaf mussels grow up to four inches long. They

have thick shells that are greenish brown, chestnut, or dark brown in color.

Their shell, like that of a few other native freshwater mussel species, has

several rows of bumps running from the hinge (umbo) to the edge of the

shell. The patterns of these rows of bumps, or tubercles, help biologists

differentiate this from other, similar mussel species. Faint rays are visible

in small shells.

Range - The range of the winged mapleleaf once included 13 states where it

was found in large rivers and streams that flow into the Mississippi River

and in one river that flows into the Missouri River. Today it is only found in

the St. Croix River on the border between Minnesota and Wisconsin.

Habitat - The one remaining population of winged mapleleaf is found in riffles

with clean gravel, sand, or rubble bottoms and in clear, high quality water.

In the past, it may also have been found in large rivers and streams on mud,

mud-covered gravel, and gravel bottoms.

Feeding Habits - To feed, the winged mapleleaf siphons in water and filters - 

out food particles. It is thought that most of the particles that are actually

used as food are phyto- and zooplankton – tiny organisms that drift with

river currents.
Why is the winged

mapleleaf

endangered?

What is being done to

prevent extinction of

the winged mapleleaf?

What can I do to help

prevent the extinction of

species?

Updated May, 2001

U.S. Fish & Wildlife Service

1 Federal Drive

Fort Snelling, Minnesota 55111-4056

612/713-5350

http://midwest.fws.gov/endangered

What is the winged

mapleleaf? (cont’d.)

Reproduction - Winged mapleleaf reproduction is similar to many other freshwater

mussels. The males shed sperm into the water. Eggs on the gills of females are

fertilized when sperm is collected as the female siphons in water. After fertilization,

the females store the developing larvae (glochidia) in their gills until they’re expelled

into the river current. These glochidia must attach to the gills or fins of a fish to

complete development. Glochidia can only develop on certain species of fish which are

called host fish. The host fish for winged mapleleaf is not known, although current

research is getting close to answering this question. Glochidia continue growing on the

fish and transform into juveniles, then they drop off and land on the river bottom where

they mature into adults. The lifespan of the winged mapleleaf is not known, but the

oldest known individual in the St. Croix is 22 years old.

Catastropic Events - Because only one population of winged mapleleaf remains, a single

catastrophic event could wipe out this species. Catastrophic events that could

eliminate the winged mapleleaf include a toxic spill, a severe drought, or disease.

Zebra Mussels - Zebra mussels are an exotic species of mussel that threaten

freshwater mussels in the Mississippi River watershed. Zebra mussels were

inadvertantly introduced into North America during the late 1980’s and became

established in the lower St. Croix River in 2000. They attach to any hard surface and

breed so prolifically that they smother or otherwise harm native freshwater mussels. It

is essential to the conservation of winged mapleleaf mussel that zebra mussels are not

allowed to invade this species’ sole remaining habitat.

Land Use Changes - The remaining population of winged mapleleaf is near the major

metropolitan area of Minneapolis and St. Paul, Minnesota. As sprawl from this urban

area continues, more and more of the St. Croix River watershed will be developed,

which could result in increasing levels of contaminants and sediments in run-off that

drains into the river.

Listing - The winged mapleleaf was added to the U.S. List of Endangered and

Threatened Wildlife and Plants on July 22, 1991. It is illegal to harm, harass, collect, or

kill the mussel. Scientific studies with winged mapleleaf or take that is incidental to an

otherwise legal activity may be allowed by obtaining a permit from the U.S. Fish and

Wildlife Service.

Recovery Plan - A recovery plan has been prepared for the winged mapleleaf. It

 identifies and prioritizes actions that are necessary to recovery this species.

Habitat Protection - Xcel Energy, which operates a dam just upstream of the only known

population of winged mapleleaf, is coordinating with the Minnesota and Wisconsin

DNR’s and the U.S. Fish & Wildlife Service to insure instream flow levels that protect

this mussel. In addition, the National Park Service, the states of Minnesota and

Wisconsin, the U.S. Army Corps of Engineers, and others are cooperating with the U.S.

Fish and Wildlife Service to keep zebra mussels out of habitat occupied by winged

mapleleaf in the St. Croix River.

Learn - Learn more about the winged mapleleaf and other endangered and threatened

species. Understand how the destruction of habitat leads to loss of endangered and

threatened species and our nation’s plant and animal diversity. Tell others about what

you have learned.

Join - Join a conservation group; many have local chapters.

Protect – Protect water quality by minimizing use of lawn chemicals (i.e., fertilizers,

herbicides, and insecticides), recycling used car oil, and properly disposing of paint and

other toxic household products. If you boat, do whatever you can to prevent spreading

zebra mussels within or between water bodies.