Friday, April 10, 2009

Clams are more interesting than you might think

Today was a great day to be in a stream. And I was, in the Big Darby Creek just southwest of Columbus. The Darby Creek system is one of the finest, most biodiverse river systems remaining in the Midwest, and there are scores of interesting critters in the water. I was really fortunate to get to spend time with some of the state's top aquatic ecologists, and not only do they know where to find the goodies and what they are when they see them, they also know lots of natural history.

Our primary targets were fish, darters specifically, and I got lots of good shots of those. I blogged about Darby darters here, here, and here, but today's photos are improved over those earlier efforts. I'll stick some up soon.

But, we saw lots of freshwater mussels, too. These, on the surface, are nowhere nearly as interesting as darters, or nearly any other animal for that matter. But wait! There's more to the story.

Probably no group of animals in Ohio, and much of the Midwest, has been hammered as badly as mussels. Something like 70% of the 80 or so species documented in the state are now listed as endangered, threatened, or special concern. Why? Because they are so sensitive to changes in the delicately balanced underwater world in which they live. Too much siltation enters the stream, and these bottom-dwellers get smothered. Protection of our best remaining rivers like the Darbys is imperative if we are to ensure mussels survive and thrive.

The above is a Kidneyshell, Ptychobranchus fasciolaris, which is still abundant. This one is alive; one of our sharp-eyed scientists spotted it through the clear waters.

This is how most people find mussels. Old, dead shells on gravel bars. They are rocklike and probably last for decades. This shell is actually very fresh, probably less than a year has passed since the critter died. It is a Spike, Elliptio dilatata, another common species. Doesn't look like much from above.

Open it up and there's another story. Shiny and lustrous purple, this glossy nacre was the downfall of many a mussel. They were once harvested in vast numbers for the pearl industry. Some poachers still try. In the last ten or so years, The Ohio Division of Wildlife has made busts of nighttime poachers in the Muskingum River dredging up scads of mussels.

Now, if you find one of these shells in Ohio, and you know your stuff, you'll know you are along a special stream. This is the long dead husk of a Rabbitsfoot, Quadrula cylindrica, an endangered species in the state. Big Darby still has populations but they are gone or nearly so in Little Darby.

A researcher plumbs the depths, looking for mussels with the aid of a viewfinder. Basically a can or container with a clear glass bottom, it eliminates surface riffles and allows pristine views of the stream bottom, where the mussels lurk.

And Bingo! We've got a homerun. This is among the rarest of the rare, a Northern Riffleshell, Epioblasma rangiana, a Federally Endangered species. This is a female, under about two feet of water, and she's "displaying". And this is where these stonelike beasts get interesting. You see, they require fish for part of their reproductive cycle. She is displaying a white flaplike chunk of tissue, in an attempt to lure a darter.

If an inquisitive potential host, such as this Greenside Darter, Etheostoma blennioides, is attracted, it will sidle up to the riffleshell. If it is really smitten by the clam's lure, it'll lunge out and try and take a bite.

If we had a camera mounted within the riffleshell, this would probably be the darter's last expression before the mussel sprung into action. You see, as soon as the darter attempts to grab a chunk of mussel tissue, the riffleshell clamps down with incredible speed and force on the darter's head! Thus captured, the writhing darter, with no hope of escape, is forcefully blasted with a spray of glochidia, or larval clams. These lodge firmly within the darter's gills, and will mature there to a point where they can drop free and begin life on the stream bottom. After the darter has been thoroughly inoculated, the mussel releases it. What a way to reproduce!!!

I want to thank Mac Albin, Anthony Sasson, Brian Zimmerman, and Tom Watters for sharing their knowledge of Big Darby Creek and its interesting animals today. The U.S. Fish & Wildlife Service deserves major kudos for working to restore the imperiled Northern Riffleshell to the waters of Big Darby. They have released severl hundred into appropriate habitat, and the early prognosis is that the mussels are doing well.

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5 comments:

dAwN said...

Interesting stuff...That darter fish is gorgeous...great coloring. I would love to capture photos like that..but I wont be putting my camera underwater any time soon. I just dropped it today into some water and thought it would never work again..so far its working.

Anonymous said...

Hi,
The darters and mussles are certainly interesting but how about next trip to the Darby you boys put on your speedos and showing us some real muscles!!!!! Ha! Ha!

Spring is in the air-what can I say! Perhaps I should clam up and dart back to work.

Happy Spring!

Jim McCormac said...

I'd remain anonymous if I made a comment like the one above, too! :-)

Susan Gets Native said...

We have bright GREEN fish in OHIO????
I need to get me some hip waders!
And I never comment as Anonymous, but I agree....Speedos would "peak" the interest in Ohio's lakes and streams!

Anonymous said...

Well,i have a bunch of clams and they are awesome!The ones i have are alive and amazing...they live in my little "river".