A diverse array of freshwater mussels in the American Southeast may be the most spectacular species you’ve never heard of.
S ome fine morning this summer, in the last remnant of free-flowing water along the Ohio River, a few surviving males of the orange-footed pearly mussel — known to friends and family as the orangefoot pimpleback — will release their sperm into the water. If fate shines on the pimplebacks, these sperm will be siphoned into the gills of nearby females, where larvae will develop.
Trickery then comes into play as female mussels use their lures to summon a host fish. Mussel lures — which can resemble juvenile fish, crayfish, insects or worms but are actually fleshy tissues of the mussel itself — are one of nature’s most spectacular examples of feminine wiles.
When a spellbound fish attempts to eat the lure, a female mussel will shoot her parasitic larvae into its mouth. Perfectly formed tiny mussels will develop on the host’s gills before dropping off to seek their fortunes; if the minuscule mussels happen to drop into unsuitable habitat, they will perish. This drama played out brilliantly for millions of years before people drastically altered mussels’ river homes. Now the balance has been tipped: Dams have changed water flow and sediment and can separate mussels from the hosts they need to reproduce; murk from sedimentation can make it impossible for potential host fish to see a mussel’s lure; and silt can smother these mostly sedentary creatures, who may close their irritated siphons and wait for conditions to improve — sometimes in vain.
The rivers and streams of the Southeast boast a stunning variety of freshwater mussels — the vast majority of about 300 recognized species in the United States — with a wide array of odd shapes, colorful bodies and shells, and even more colorful
names: Cumberland monkeyface, rough pigtoe, winged spike, fluted elephantear, pistolgrip.
They play a significant ecological role, providing food for fish, crayfish, amphibians, turtles, birds and mammals. Mussels constantly filter water through their bodies, which improves water quality. Unfortunately, they also accumulate toxins just by breathing and feeding, and they are particularly sensitive to pollutants such as pesticides, fertilizers and heavy metals.
By nature, mussels lead long lives, some exceeding 100 years, giving them the longest lifespan of any freshwater invertebrate. But now, due primarily to habitat loss and degradation, at least 35 U.S. species have already gone extinct, while most remaining freshwater mussel species are in imminent danger of extinction.
One of those hanging in the balance is the aforementioned orangefoot pimpleback: Once found in nine states from Alabama to Pennsylvania, it now clings to life and reproduces in only two populations. Though it has been federally protected under the Endangered Species Act since 1976, the U.S. Fish and Wildlife Service continues to allow destructive projects to harm its habitat.
The Center is working to fight a proposed marina in Kentucky’s Ohio River that would fill in nearly eight acres of a significant mussel bed that is home to the orangefoot pimpleback and four other endangered or proposed endangered mussel species: the fat pocketbook, pink mucket, sheepnose and spectaclecase. •
ierra Curry hails from Kentucky and is a conservation biologist in the Center’s Flagstaff, Ariz., office. She heads up our campaign to fight Southeast freshwater species extinction.