Endangered Species Series: Mussels

In this installment of our endangered species series, Michele Skalicky talks with a Missouri State University professor about studies underway to help Missouri's mussels.

Sound of river

Along MO lake and river bottoms live fascinating creatures, mussels. There are around 60 different kinds in the state. Six are listed as endangered. One species is believed to be extinct now—the Curtis Pearly Muscle.

Sound of lab at MO State

Researchers at MO State University are working to learn more about mussels in an effort to save those that are in trouble.

On a recent summer day, a student was in a lab at Temple Hall working on the propagation of a threatened species of native mussel—the Neosho Mucket. He would extract the larval stages—called glochidia—from the female and take them to the Chesapeake Fish Hatchery to be attached to large mouth bass. Once they reached the juvenile stage they'd be released in the Spring and Neosho Rivers in Oklahoma.

Chris Barnhart is professor of biology at MO State. He says some species of mussels use a variety of fish hosts for their larvae while others use only a certain kind of fish. Researchers at MO State are working intensively with 4 species.

"When I say intensively I mean those are the species that we're trying to propagate in large numbers, but then we're doing various kinds of research on probably a dozen other species."

The labs at MO State include an aquarium system where researchers can study the larvae on the fish hosts. Once they've attached to the fish, both glochidia and fish are moved to what look like large blue barrels.

Some of the larvae will be kept at MO State and allowed to grow larger before release into the wild so they're not as likely to be eaten by predators.

The MO State University biology department has been doing recovery work of mussels since 1998. According to Barnhart, Missouri State researchers are the first to grow mussels until they reach sexual maturity. He says that will allow them to learn even more about these creatures.

"One of the best things that's happened because we've learned how to grow these animals is that now we've got lots and lots of uniform-aged individuals that can be used for experiments, in particular, toxicology experiments so we can find out how sensitive they are to ammonia or chlorine or copper, and they are very good indicator species for certain kinds of polllution."

Why should we care about what happens to our mussels? For one thing, Barnhart says they can tell us a lot about the quality of our water.

"When mussels are present, that's a very good sign that a lot of things are right. When mussels are absent, it's a sign that one of dozens of different things could be wrong, so their absence doesn't tell you very much about what's wrong, but their presence tells you that a lot of things are right."

According to Barnhart, some species of mussel that are doing poorly in other parts of the United States, including the Spectacle Case, are thriving in the Ozarks.

"That mussel is doing very well in the Meramec and the Gasconade Rivers in Missouri, and it's been nearly entirely lost in other parts of the country. Why is it doing well here and being lost everywhere else? Don't know. It probably has something to do with water quality, but it might have to do with the fish host. We don't know what the fish host is yet, but at least here we've got opportunities to study it and try to find out what its life cycle is and then we might be better able to understand why it's doing well here and not other places."

He suspects that may be due to the fact that there's not much row-crop agriculture in this part of the nation and the fact that the area's not as urbanized as it could be.

Mussels were once the reason for a thriving industry in Missouri a little more than a century ago. They were harvested in huge numbers, and their shells used to make buttons. In fact, a multi-million dollar button manufacturing industry was located in the state.

Mussels have some unusual and interesting names including Pink Heelsplitter, Fawnfoot and Fat Pocketbook.

"Their names were given to them by the clammers, the guys who harvested the shells for button culture back when."

Over harvesting during the height of the button making industry in the state hurt mussel populations.

Today, the major culprit for the decline of certain mussel populations is habitat destruction.

Amazingly enough, certain types of mussels can live for a century, others only 2 or 3 years. The average, according to Chris Barnhart, is a couple of decades.

He says mussels have become very accomplished anglers.

"They've got incredible adaptations to lure fish and infect their gills with these tiny baby mussels."

Some mussels have special adaptations to attract fish—they have lures that look very much like small fish, crayfish and insects. The fluted kidney shell mussel has a lure that looks very much like the pupal stage of the black fly, an important food source for darters and other small fish that live on the bottom of rivers.

"And this structure, which is a dead ringer for a pupal black fly, is actually a bag of glochidia, and if a darter strikes it and bites it, it'll break open and break open the glochidia."

Chris Barnhart says he's amazed at how unbelievably adapted mussels are to allow them to reproduce.

To find out more about mussels, go to unionid.missouristate.edu.

Join us tomorrow morning at 7:33 as we look at another endangered species...the hellbender salamander.

These stories are available on the web at ksmu.org. For KSMU news, I'm Michele Skalicky.