Rayed Bean Fact Sheet

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					                                            U.S. Fish & Wildlife Service

                                          Rayed Bean (freshwater mussel)
                                          Vilosa fabalis
The rayed bean is a freshwater
mussel that the U.S. Fish and
Wildlife Service has proposed to list
as an endangered species.
Endangered species 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
are primary objectives of the U.S.

                                                                                                                        Photo by USFWS
Fish and Wildlife Service’s
endangered species program.

What is the Rayed Bean?
                                          The rayed bean, a small freshwater mussel of the upper Midwest and Eastern
Appearance: The rayed bean is a           United States, has been proposed for listing as an endangered species.
small freshwater mussel, usually
less than 1.5 inches long. Its shell is
smooth-textured and green,                but they are sometimes found in           of a specific host fish species to
yellowish-green, or brown with            large rivers and wave-washed areas        complete development into juvenile
numerous dark-green wavy lines.           of glacial lakes, including Lake Erie.    mussels. If successfully attached to
The male’s shell shape is generally       They prefer gravel or sand                a host fish, glochidia mature into
elongated, whereas the female’s is        substrates, and are often found in        juvenile mussels within a few weeks.
smaller and elliptical.                   and around roots of aquatic               They then drop from the fish and
                                          vegetation.                               continue to grow, if they fall onto
Range: The rayed bean historically                                                  appropriate substrate. Using fish as
was found across a wide expanse           Adults spend their entire lives           a host species allows the rayed bean
that included parts of the Midwest,       partially or completely buried in         to move upstream and populate
the eastern United States, and north      substrate, filtering water through        habitats it could not reach otherwise.
to Ontario, Canada. Once found in at      their gills to remove algae, bacteria,
least 112 streams, canals, and lakes,     detritus, microscopic animals, and        What threatens the rayed bean
the rayed bean now occurs in only 28      dissolved organic material for food.      mussel?
streams and 1 lake; a 75 percent                                                    Dams: Dams affect both upstream
reduction in the number of occupied       Reproduction: The life cycle of the       and downstream mussel populations
streams and lakes. The species has        rayed bean, like most freshwater          by disrupting natural river flow
been extirpated from Illinois,            mussels, is unusual and complex.          patterns, scouring river bottoms,
Kentucky, Tennessee, and Virginia         The male releases sperm into the          changing water temperatures, and
but is still found in Indiana,            water column that is then siphoned        eliminating habitat. The rayed bean,
Michigan, New York, Ohio,                 by the female to fertilize her eggs.      a mussel adapted to living in flowing
Pennsylvania, West Virginia and           Fertilized eggs develop into              water habitat, cannot survive in the
Ontario, Canada.                          microscopic larvae, called glochidia,     still water impounded behind dams.
                                          within special gill chambers. Female
Habitat: The rayed bean generally         mussels expel mature glochidia,           The rayed bean also depends on host
lives in smaller, headwater creeks,       which must attach to the gills or fins    fish as a means to move upstream.
Because dams block fish passage,        sedimentation also reduces feeding       planning for recovery and recovery
mussels are also prevented from         and respiratory ability for the          actions.
moving upstream, which isolates         snuffbox mussel, which can lead to
upstream mussel populations from        decreased growth, reproduction, and      Watershed Protection through
downstream populations leading to       survival.                                Partnerships: The rayed bean
small unstable populations more                                                  cannot survive without help from
likely to die out.                      Nonnative Species: Nonnative zebra       watershed partnerships to restore
                                        mussels have invaded U.S. waters,        habitat and improve surface lands.
Pollution: Adult mussels are easily     and pose a serious threat. Zebra         Causes of habitat degradation are
harmed by toxins and degraded           mussels proliferate in such high         numerous in streams throughout its
water quality from pollution because    numbers that they use up food            range. In many cases, the threats
they are sedentary (they tend to stay   resources and attach to native           are not from actions in or adjacent to
in one place). Pollution may come       mussel shells in such large numbers      the rivers where the species is
from specific, identifiable sources     that the native mussel cannot eat or     found. Instead, threats are due to
such as accidental spills, factory      breath.                                  widespread problems on uplands at
discharges, sewage treatment plants                                              the highest elevations of watersheds.
and solid waste disposal sites or       Another invasive species, the round      Habitat restoration will require
from diffuse sources like runoff        goby, is a nonnative fish that may       improvements across the entire
from cultivated fields, pastures,       displace native host fish species,       watershed. The voluntary assistance
feedlots, farms, mines, construction    thus reducing reproductive ability of    of Federal and State agencies,
sites, private wastewater discharges,   the snuffbox reproduce.                  conservation groups, local
and roads. Contaminants may                                                      governments, private landowners,
directly kill mussels, but they may                                              industries, businesses, and farming
                                        What is being done to conserve and       communities will be necessary to
also reduce water quality, affect the   restore snuffbox mussels?
ability of surviving mussels to have                                             meet recovery goals.
young, or result in lower numbers or    Listing: In 2004, the U.S. Fish and
disappearance of host fish.             Wildlife Service designated the          What can you do?
                                        rayed bean mussel as a candidate
                                                                                 Learn more about how the
Sedimentation: Sedimentation can        species for listing as threatened or
                                                                                 destruction of habitat leads to loss
be accelerated by poor land use         endangered under the Endangered
                                                                                 of endangered and threatened
practices, dredging, impoundments,      Species Act. The Service is now
                                                                                 species and our nation’s plant and
intensive timber harvesting, and        proposing to list it as endangered. If
                                                                                 animal diversity. Discuss with
heavy recreational use. Excessive       listed, the rayed bean will receive
                                                                                 others what you have learned.
sedimentation suffocates freshwater     the full protection of the Endangered
mussels because it is difficult for     Species Act (ESA). The ESA would
                                                                                 Help improve water quality locally
them to move away from the threat.      provide protection against certain
                                                                                 in streams by minimizing use of
Impacts from increased or heavy         practices and would require
                                                                                 lawn-care chemicals and properly
                                                                                 disposing of or recycling hazard-
                                                                                 ous materials found in your home,
                                                                                 like batteries, paint, car oil, and

                                                                                 When boating, please follow any
                                                                                 rules established to prevent the
                                                                                 spread of exotic pests like the
                                                                                 zebra mussel.

                                                                                 Join a conservation group or
                                                                                 volunteer at a local nature center,
                                                                                 zoo, or wildlife refuge.

                                                                                 U.S. Fish & Wildlife Service
                                                                                 1 Federal Drive
                                                                                 Fort Snelling, Minnesota 55111

                                                                                 October 2010

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