Snuffbox and Rayed Bean Mussels: Freshwater Species of the Week

A rare freshwater snuffbox mussel (Epioblasma triquetra), now protected as an endangered species. Photo: Joel Sartore


Two colorfully named freshwater mussels received protection under the Endangered Species Act this week: the snuffbox and rayed bean.

As NG Freshwater Fellow Sandra Postel has pointed out before, freshwater mussels as a group are among the most critically endangered species in North America.

Although they have long served as an important food source for a wide variety of animals (including people), freshwater mussels are highly sensitive to poor water quality and large-scale changes in the flows of rivers. As we have altered and polluted rivers, freshwater mussels, which live by filtering tiny bits of food out of water, have been hard hit.

Besides depriving other animals of a high-quality food source, the loss of freshwater mussels has further harmed water quality because the animals filter out pollutants over time.

The snuffbox (Epioblasma triquetra) is a medium-sized, yellow mussel with triangular-shaped females and oval-shaped males.  It tends to live in small to medium-sized creeks with a swift current, although it is also found in Lake Erie and in some larger rivers.

The snuffbox was formerly common in Alabama, Arkansas, Illinois, Indiana, Kentucky, Michigan, Minnesota, Missouri, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Wisconsin. But it has declined by more than 60 percent in recent years and has disappeared entirely from four states. Conservation advocates have sought endangered species protection for the species since at least 1991.

Also appropriately named because of its shape, the rayed bean (Villosa fabalis) is a small (less than 1.5 inches long), shiny, greenish mussel with wavy stripes. The rayed bean is most often found on gravel or sand, often around roots of aquatic plants. It tends to live in headwater creeks, though also has been found in Lake Erie and larger rivers.

The rayed bean mussel was once found in 10 states, from Tennessee north into Canada, but it has declined by more than 70 percent and is now found only in small groups in Tennessee, West Virginia, Indiana, Ohio, Michigan, New York, and Pennsylvania. It was placed on the waiting list for the Endangered Species Act in 1984.

Photo: Rayed bean mussel
Rayed bean mussel. Photo by USFWS; Angela Boyer


The Center for Biological Diversity helped pave the way for listing of the mussels by putting pressure on the federal government. Last July, the advocacy group struck a legal settlement with the U.S. Fish and Wildlife Service that required the agency to decide on whether to list hundreds of plants and animals as endangered by 2018.

Among other species affected by the settlement are 374 Southeast freshwater species, 35 springsnail species, the Ozark hellbender, 26 Pacific Northwest mollusks, eight Southeast freshwater mussels, and 23 species native to Oahu.

In a press release, Tierra Curry, a conservation biologist at the Center for Biological Diversity, said, “We’re so excited these mussels now have the protection they need to stave off extinction. The Endangered Species Act has prevented extinction for 99 percent of the species it protects, so at last the snuffbox and rayed bean have a real chance of survival and recovery.”

The advocacy group hopes that the Fish and Wildlife Service will take the next step of designating critical habitat for the new endangered species, which could lead to specific enforcement of protected areas, and possibly restrictions on harmful activities like pollution.


Brian Clark Howard is a writer and editor with He was formerly an editor at The Daily Green and E/The Environmental Magazine and has contributed to many publications, including,,,, Yahoo!, MSN and elsewhere. His latest book, with Kevin Shea, is Build Your Own Small Wind Power System.