Out-Musseled

I’ve gotten violently ill from eating mussels in the past. Then again, I’ve gotten violently ill from ingesting a lot of things, including muddy crayfish, melted mango sorbet, and the tap water in Davis, West Virginia. But mussels are usually a prime suspect if you find yourself with a gurgling stomach after a seafood dinner. Since they’re shelled and on the smaller side, restaurants often aren’t diligent in checking each mussel. And if a mussel is open before being tossed in the pot – even just a crack – it’s likely already spoiled.

It’s important to differentiate the mussels that are a common form of food poisoning from their distant cousins, the freshwater mussels. Freshwater mussels actually have the potential to make you doubly sick if you eat them (which you shouldn’t because it’s illegal, but more on that later). Like saltwater mussels, freshwater mussels can go bad inside their shells before they’re cooked, but they also filter out pesticides and heavy metals from our incredibly polluted lakes and rivers, so ingesting enough of them would probably cause some sort of long-term-chronic-disorder-disease-disagreement.

At this point you’re putting together the pieces and trying to guess how many freshwater mussels I’ve eaten recently. And the answer, for legal as well as practical reasons, is zero. Yet for much of Minnesota’s history, freshwater mussels were an important food source. Native Americans across the country dug them out of the silty, sandy shallows, eating their delicious meat and using their shells for tools and jewelry. In the 1890s, some German guy started harvesting the mussels in Iowa, throwing out their meat, and making buttons out of their shells. The Midwest became a button-making hub, and with the addition of wandering pearl-hunters, oxygen-depleting dams, and invasive species, mussel populations plummeted.

Today, 56% of mussel species native to Minnesota are at risk of extinction. Kneeling at the bank of Minnehaha creek, I knew this fact vaguely, but at that moment, all I saw was an awesome creature who would get along swimmingly with my tadpoles. The mussel was brown, the size of a closed fist, and it sported an unkempt beard of filamentous algae. It looked just like a clam, which is what I called it at first, but which I know now isn’t the technical term.

I also knew the mussel was a filter-feeder and would do great things for the water quality of my newly filled aquarium. I picked it up and popped it in a mason jar already filled with creek water. Now, for any DNR Game Wardens reading this, I am issuing this disclaimer:

The contents of this post are not verifiably true. If any events described herein resemble real events, it is entirely coincidental. I have never harmed a freshwater mussel. I have never eaten a freshwater mussel. There are no freshwater mussels in my bathtub, on my person, or in the trunk of my car.

On their website, the DNR says that no live mussels can be collected in the state of Minnesota. Interestingly, you are allowed to possess up to 24 mussel shells, as long as you have a fishing license (which I do). This of course brings up an interesting situation in which someone could legally kill a mussel – up to 24 of the poor guys – just to keep their shells. Perhaps it’s legislation leftover from the rampant button making industry of the early 20th century. Even more interestingly, the DNR reminds us that it’s “illegal to collect state listed species” but doesn’t specify if there is any law pertaining to the 44% of mussel species that aren’t state listed. These are all helpful notes for my lawyer to think about in the unlikely event that the DNR gets enough funding to investigate my (alleged) mussel abduction.

Once home, I placed the mussel in her new home, and she almost immediately began exploring, happy as a clam (ha ha). Mussels have a muscular “foot” which they use to scoot themselves across the streambed and dig themselves into sandy areas. Within an hour, she had crisscrossed the aquarium, digging little trenches in the substrate, before eventually finding a suitable spot to open up and begin feeding.

A snail and tadpole work together to clean the shell of the mussel.

It’s not often that one gets an opportunity to watch a freshwater mussel feed. Growing up, I would find mussels in Lake Wingra, using my toes to feel them out on the lake bottom. I’d lift them up quickly, marveling as the mussel’s muscular foot would retract into its shell. Then my brother and I would play a game called “Mussel Attack” where I would lob mussels at him and he would try to escape before they splashed back into the water near his head. Needless to say, the mussels weren’t exactly in high spirits during these interactions. So, when my newly acquired mussel opened up and began to feed, I was glued to the glass of the aquarium.

Her mouth – or “incurrent siphon” – was right next to her butt – or “excurrent siphon”. This is not gross at all when you remember that the diet of a mussel is essentially just seasoned water. Water is sucked in through the incurrent siphon, and passed through a set of internal gills, where nutrients and plankton are filtered out. Then the water is pushed out the excurrent siphon.

Just beneath the siphons, I noticed a huge flap of mussel-flesh emerge. I was startled to observe two eyeballs on this waving, gray extrusion. At least they looked like eyeballs: on closer observation they turned out to be decoy eyes. Stepping back, the whole appendage resembled a twitching, bright-eyed minnow. I was flabbergasted. A mussel with a built-in fish lure? What was next? Flying pigs? Fish with built-in mussel lures?

The mussel displays her fish lure!

That’s when I started to do some research. I learned that my mussel was a Plain Pocketbook Mussel, easily identified by her fish lure. There are several other mussel species that sport a lure, but none are quite as spectacular as that of the Plain Pocketbook. Only when I read further did my stomach begin to gurgle, and I started to wonder if I had perhaps ingested a bad mussel for lunch.

Mussel lures are not a defense mechanism, or even a way to somehow attract food. They’re actually an essential piece of mussel reproduction . It goes like this: the male mussel sprays a bunch of sperm into the stream, where it mixes with the current and hopefully is filtered out by a female mussel. Her eggs fertilized; the female simply must send more baby mussels downstream. Right? Wrong. That would mean that mussels could only ever spread downstream, and never up. How would they colonize new water courses?

Evolution found a way. A weird way, but a way. Instead of ejecting her babies into the ether, the mama mussel holds onto them, letting them grow to larval state in a little pouch. On either side of the pouch, are flaps of flesh, sporting fake eyes. Twitched just right, her lure should attract the attention of a large fish. Maybe a bass, or an extra-chunky bluegill.

The bass strikes! But instead of a tasty snack, he’s instantly enveloped in a violent ejaculation of mussel-larvae. The baby mussels, like thousands of miniature plastic chip-clips, snap onto the gills and mouth of the fish. Over the next month or so, the babies will suck blood from the fish, growing nice and big and strong. Thus transformed, they’ll hop off the fish and land in a totally different part of the stream.

An excellent video of how mussel reproduction works. The mussel shown is a closely related species.

“Isaac,” I said, “We need to do an experiment.”

My idea was simple: take the mussel down to the lake, place it on the lakebed right next to my GoPro camera, and get some excellent footage of mussel-parasitism in action. Isaac and I discussed a back-up plan: catch a bass and put it in the bathtub with the mussel and the GoPro in a more controlled environment. Isaac agreed that the experiment would be epic and so we biked down to the lake one sunny afternoon to do some science.

I won’t kill you with unnecessary suspense. The experiment failed. While there were plenty of fish around, the mussel decided to keep her lure inside her shell, and instead buried herself all the way in the sand. I got about 30 seconds of mildly interesting bluegill footage. Isaac and I briefly discussed Plan B(athtub) but decided against it. During my research, I had discovered that not only were freshwater mussels incredibly important for water quality, but that kidnapping them and putting them in your aquarium was probably illegal.

It was time then, to return our new friend to her home in Minnehaha Creek. She had done us a great service, filtering the water in the aquarium through her gills at least twice (mussels filter about 1/3 gallon per hour). In return, we had taken her on an enriching field trip, and the tadpoles had nibbled off her scraggly beard of algae. Isaac and I walked down to the creek – the water was high from recent rains. We looked for a spot to put her safely, and there! A whole school of flashing creek chubs. We plopped her in, right over the heads of the unsuspecting fish. As long as her shell was closed, the fish were safe. But in an hour, or half a day, when they went to investigate the twitching minnow on the streambed, they would be in for quite the surprise.

Isaac says goodbye to the mussel.