Higgins' eye pearlymussel is 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 is the primary
objective of the U.S. Fish and Wildlife Service's endangered species
is the Higgins' eye pearlymussel?
Name - Lampsilis higginsi
Appearance - Higgins'
eye pearlymussel is a freshwater mussel with a rounded to slightly
elongate smooth-textured shell that is usually yellowish brown with
green rays. The shell, made up of 2 hinged, inflated halves, is up to
4 inches in length and has a rounded side and a pointed (males) or
squared (females) side. The inside of the shell is white with portions
that are iridescent and areas that may be tinged with cream or salmon.
The soft body enclosed by the shell consists of gills for breathing, a
digestive tract for processing food, and a large muscled foot for
moving the animal.
Range - Higgins'
eye pearlymussels are now found in parts of the following rivers: the
upper Mississippi River north of Canton, Missouri, and in 3
tributaries of the Mississippi River - the St. Croix River between
Minnesota and Wisconsin, the Wisconsin River in Wisconsin, and the
lower Rock River between Illinois and Iowa. The species' current range
is about 50% of its historic distribution. Even within its current
range it formerly was more widespread and abundant, occurring as far
south as St. Louis, Missouri, and in several additional tributaries of
the Mississippi River.
Habitat - The
Higgins' eye is a freshwater mussel of larger rivers where it is
usually found in areas with deep water and fast currents. The animals
bury themselves in the sand and gravel river bottoms with just the
edge of their partially-opened shells exposed. The river's currents
flow over the mussels as they siphon water for microorganisms such as
algae and bacteria, which they use as food. The role of Higgins' eye
pearlymussels in the natural river ecosystems is as a food source for
wildlife like muskrats, otters, and raccoons and as a filter which
improves water quality.
- The male Higgins’ eye releases sperm into the river current
and downstream females siphon in the sperm to fertilize their eggs.
After fertilization, the females store the developing larvae (glochidia)
in their gills until they’re expelled into the river current. Some
of the glochidia are able to attach themselves to the gills of host
fish, where they develop further. After a few weeks, the juvenile
mussels detach from the gills of the fish and settle on the river
bottom, where they can mature into adult mussels and possibly live up
to 50 years. The sauger, walleye, yellow perch, largemouth and
smallmouth bass, and freshwater drum are considered suitable hosts for
Higgins’ eye glochidia.
is the Higgins' eye pearlymussel endangered?
Habitat Loss or Degradation - Higgins’ eye pearlymussels
depend on deep, free-flowing rivers with clean water. Much of their
historic habitat was changed from free-flowing river systems to
impounded river systems. This resulted in different water flow
patterns, substrate characteristics, and host fish habitat and
movement which affect how the Higgins’ eye feed, live, and
reproduce. Municipal, industrial, and farm run-off degrade water
quality. As a filter-feeder, this species concentrates chemicals and
toxic metals in body tissues and can be poisoned by such chemicals in
the water. Dredging and waterway traffic produce siltation which cover
the substrate and mussel beds.
Exotic Species - The zebra mussel is a freshwater mussel
native to the Black and Caspian Seas that was introduced into Lake
Erie in the late 1980’s from ship ballast water discharge. This
small mussel is less than 2 inches in length, but tens of thousands
can colonize a square meter area. They attach to any hard surface,
including shells of other mussels. They compete for food with native
species and, when attached to the shells, prevent normal travel,
burrowing, and opening and closing of the shells.
being done to prevent extinction of the Higgins' eye pearlymussel?
Listing - The Higgins’ eye pearlymussel was added to the
U.S. List of Endangered and Threatened Wildlife and Plants in 1976. As
a result of the listing, the U.S. Fish and Wildlife Service developed
a recovery plan that describes actions needed to help this species
Research - Researchers are continuing studies of zebra
mussels and their impacts on Higgins’ eye, of commercial navigation
impacts on mussels, and of water quality and contaminant relationships
to the species.
Habitat Protection - A variety of government and private
conservation agencies are working to preserve Higgins’ eye
pearlymussel and its habitat.
I Do to Help Prevent the Extinction of Species?
Learn - Learn more about Higgins’ eye pearlymussel and
other endangered and threatened species. Understand how the
degradation and destruction of endangered and threatened species and
our nation’s plant and animal diversity. Tell others about what you
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
Follow - When boating, please follow any rules established
to prevent the spread of exotic pests like the zebra mussel.
3 Endangered Species Home Page
National Endangered Species Home
Region 3 Home Page USFWS
Fish and Wildlife Service
Division of Endangered Species
BHW Federal Building
1 Federal Drive
Fort Snelling, Minnesota 55111-4056