Fresh Water Mussels - Better than a Rock

By Robin Engelking
As published in Aqua News, Minnesota Aquarium Society, July/August 1999.
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Mussels can be found in most bodies of water: rivers, streams, lakes and ponds. Minnesota has a number of species of mussels in each of the classes of endangerment, but they are all stream dwelling animals. If you collect your animals from a lake or pond you will either find Anodonta grandis (Common floater) or Lampsilis siliquoidea (Mucket). Both species are very common. To collect mussels all you need is a fishing license and a good eye. Mussels are almost always partially buried in the substrate with only the posterior portion exposed.

To identify a living mussel you need to know the names of some of its external features.  The umbo is the most inflated part of the valve (shell). It is also called a beak and is very useful in identifying your mussel. Many mussels are tan, brown or black and many shades in between. Some have colored rays or other features like bumps left (tubercles) or ridges on the shell.

The most prevalent mussel is Lampsilis siliquoidea, which can grow to 5 inches. Its smooth elongated shell is yellow or tan with green rays. The dorsal and ventral margins are usually straight and the umbo is only slightly above the hinge line. It's preferred habitat is lakes and small to medium streams. It will be found in shallow water, often near aquatic plants, in mud, sand or gravel.

The other mussel you are most likely to encounter is Anodonta grandis. As its name implies, it can get very large, up to ten inches. The smooth elliptical shell can be yellow, green or brown and it can occasionally have green rays. It has an inflated umbo that is fairly prominent with 3 to 5 double looped bars, which look rather like a "w". The anterior end is broadly rounded and the posterior end is bluntly pointed. This animal is found in most habitats including ponds, lakes and sluggish pools of creeks and rivers. It will be buried in mud or sand with just the siphons showing.

You've found your mussel and are ready to take your find to its new home. Because these animals are from Minnesota lakes, they prefer cooler water. An unheated tank is perfect. The cooler the better, but water up to 72 to 75 degrees should be fine. They will need a substrate three or four inches deep to bury themselves in. Either gravel or sand will work fine. Mussels have a top and a bottom. When you collect them it is best if you try to notice which end is up. If you can't remember just lay the animal on its side on the substrate and let it work its own way into the gravel. If you put the mussel in upside down it will smother if it can't work its way out of the gravel. Mussels are filter feeders and will keep your water sparkling clean. When they are feeding or breathing the shells (more properly called valves) gape open and you will notice two tubes sticking out of the top. The upper one is surrounded by a fringe and is called the incurrent siphon. The mussel draws water in through this organ and passes it over its gills to get oxygen and then through its stomach where it filters out microscopic critters and plants to eat. After that the water is expelled through the bottom tube which is called the excurrent siphon.

A mussel normally sits peacefully siphoning water and minding its own business. You might be thinking you know the perfect place for your new pet, but keep in mind that the mussel is mobile. If it doesn't like where you put it, it will move. It can uproot plants and move rock or other tank decor in the process. Often if a mussel starts roaming around the tank it is a sign that something is wrong. The mussel is trying to get to better water. Check your ammonia and nitrate levels and check the temperature. If the water gets too hot mussels often try to leave the area.

As long as you have fish in the tank and you feed the fish the mussels will get some food. If you want you can supplement them with a powdered food for marine filter feeders or APR once a week or so. Use an eyedropper or something similar to get the food close to the mussel.

Freshwater mussels can be an interesting and unusual addition to your cold water tank. One of the best things about them is collecting them yourself. You really come to appreciate the animal when you get yourself wet too.

Bibliography:

1. Cummings, KS and C.A. Mayer, Field Guide to Freshwater Mussels of the Midwest. Illinois Natural History Survey Manual 5 1992

2. Fuller, Samuel, Freshwater Mussels of the Upper Mississippi River. Wisconsin Department of Natural Resources 1985