‘From the brink’
Purple cat’s paw mussel claws back
You cannot talk with biologists about mussels without delving into the shelled creatures’ sex lives. We’re not discussing impassioned grappling on a stream bed, either. No. For mussels to thrive, they need more inducement than a come-hither glance, the music of moving water.
Sometimes they need scientists — one in a snorkeling mask, another with a mixture containing rabbit blood.
Let us go to Killbuck Creek, an Ohio stream that curls through wood and field until it finds the Wahonding River, a tributary of the Ohio River. Twenty-plus years ago, a professor searching the creek for a particular fish species found something else: a population of Epioblasma obliquata obliquata, the purple cat’s paw mussel.
In the world of mussels, this was a big deal. The purple cat’s paw once was found throughout the Ohio River basin. But declining water quality decimated the population to the point that some biologists assumed it was as dead and gone as the ivory billed woodpecker, a big bird that ornithologists still seek in the swampy flatlands of the South. It has achieved mythic status. In a comparable way, so had the purple cat’s paw. The federal Endangered Species Act lists it as endangered, the most critical classification.
Happily, the fish professor in Killbuck Creek knew what he held. He contacted Ohio fish and wildlife officials. Word spread in the musseling community.
Leroy Koch, a biologist with the U.S. Fish and Wildlife Service (Service), sat up and took immediate notice.
“It was an amazing, serendipitous find,” said Koch, who works in the Service’s Frankfort, Kentucky, field office. “He was looking for fish, not mussels.”
‘A funny thing’
A word here about malacologists, or mussel scientists. Some believe it’s best to leave mollusks alone and not tamper with the environment where a species might be hanging on. Others take a different tack. Why not improve their chances of survival, they ask, by helping propagate the species?
“It is,” said Koch, “a funny thing about mussel biologists.”
So, while the mussels lay in Killbuck Creek, scientists debated the merits of leaving them alone or doing something to increase the creatures’ numbers. Koch argued the latter.
A mussel fan – their beautiful shells first caught his attention as a grad student, and Koch’s fascination since then has only grown – Koch urged wildlife officials in Ohio to let the Service take a look in the creek. In 2006, Ohio said OK.
Koch dispatched a “good field biologist” to Killbuck Creek with orders to see how the population was doing. The biologist came back with glum news. “We found old, male individuals.” The search did turn up some female shells (they are smaller, and differently shaped, than male shells), but they appeared old. For some time, the guys had been on their own.
Or were they? It takes keen eyes and snorkeling gear to discern something that, full-grown, may reach 2 inches in length and is buried in sand. The creek, Koch knew, might hold a few more surprises. The Service kept looking. In 2012, that search paid off. A biologist found a female in the creek. She was gravid, the word scientists prefer over “pregnant.” Then they found a second female, just as gravid/pregnant as the first.
Koch convinced Ohio officials to let the Service remove the females and hand them over to Monte McGregor, a leader in the field of in-vitro mussel research. A Ph.D. who works for the Kentucky Department of Fish and Wildlife Resources, McGregor is the state malacologist. He’s renowned for his work using other hosts in growing young mussels.
A primer in mollusk procreation: Male mussels impregnate females by releasing sperm into the water. (In the case of the Killbuck Creek boys, you could call it the triumph of optimism over the odds – so many males, so few females.) If a female does receive the sperm, she gets busy. Fertilized, mama mussel begins nurturing the tiniest of creatures, called glochidia. They remain with the female until she can fool a fish into taking over her job.
For the female purple cat’s paw, that means opening its shell and dangling a protrusion. This usually attracts a curious fish. Perhaps that wiggling thing is edible? The fish sticks its head in the open shell. Clamp! The fish is a temporary hostage while the mussel releases glochidia in its direction. The lucky ones find a spot on the gills, rich with blood and oxygen, and they burrow in. The mussel releases her grip. The fish doubtless swims away in a panic, relieved to escape and wondering what just happened.
Two or three weeks later, the glochidia, each smaller than a grain of salt, let go of their unwitting host. They drop to a river or creek bed where they assume a life of bottom feeding and straining water. They help keep a stream clean.
Enter McGregor, who has researched cutting out the middleman – or fish — and placing the glochidia in a serum. He has had success with a number of host liquids, including a mixture comprising the serum from rabbit’s blood and other chemicals. When he got the gravid females, he put the glochidia in the host liquid in a petri dish, put that in an incubator, and waited. In 2015, he was rewarded with a healthy crop of juveniles.
“We’ve definitely done well” with the cat’s paw mussel, said McGregor.
Call it another success story for a guy who got introduced to freshwater mollusks as an undergraduate. A professor offered McGregor a job working in mussels for $3.35 an hour.
“I didn’t know much about them,” he said. “But I needed a job.”
Mussels got hold of McGregor as firmly as female cat’s paw mussels grab a fish. In addition to his role as the state malacologist, McGregor is director of the Center for Mollusk Conservation. Its purpose is self-explanatory.
Now, the Service and its partners have about 2,400 purple cat’s paw mussels – enough, said Koch, to place in rivers in Ohio, Kentucky, Tennessee and West Virginia. He, McGregor and others will place 400 this year, and the balance in 2018.
Most of the sites are places where the mussels once thrived – and Koch, hopes, will do so again.
“We’re hoping they’ll like their new homes,” he said. “They should.”
No, the mussels aren’t ready to be removed from the ESA’s list of protected fish and wildlife. But, yes, they are doing better.
“I think we can say that we’ve literally pulled the species back from the brink of extinction,” he said.
Koch, meantime, hasn’t given up on Killbuck Creek. Biologists with face masks still poke their heads into its waters, looking for a dusky-brown shell of the elusive cat’s paw mussel.
Somewhere in those tumbling waters, they think, some more mussel whoopee may be going on.
Mark Davis, Public Affairs Specialist
firstname.lastname@example.org, (404) 679-7291
The mission of the U.S. Fish and Wildlife Service is working with others to conserve, protect, and enhance fish, wildlife, plants, and their habitats for the continuing benefit of the American people. For more information on our work and the people who can make it happen, visit fws.gov. Connect with the Service on Facebook, follow our tweets, watch the YouTube Channel and download photos from Flickr.