Mussel Power

I had no idea there are around 300 freshwater mussel species in North America, making our continent the richest in the world for these animals. Most of them occur in the mighty Mississippi Basin, particularly in the southeast, but we have a few in the metropolitan area as well. AMNH has a short course on 17 species, including the dwarf wedgemussel, brook floater, yellow lampmussel, creeper, and paper pondshell.

There are some great common names among the freshwaters: turgid blossom, finerayed pigtoe, snuffbox. The Tennessee riffleshell, Scioto pigtoe, and Sampson’s pearlymussel, however, are among the estimated 3-10% of mussel species in the U.S. that have gone extinct since 1900. The culprits are the usual: development, dams, silting, pollution. Perhaps not so usual culprits are invasive zebra mussels, which grow in such profusion — 50,000 mussels per square yard — they starve and smoother native species. Until plastics took over after WWII, the pearl button industry scoured rivers and streams for the shells. During the second half of the 19th century, there was a pearl-rush, in which hopeful get-rich-quickers desperate for pearls rapaciously ripped up shoals and beds from the East coast to the Rockies. Today, the cultured pearl industry still depends on using U.S. freshwater mussel shell fragments as the seeds for their marine oyster pearls. In states where commercial collecting is illegal, poachers dreg up the mussels anyway. Did you ever wonder where your pearls came from, what connections and steps of the web of complexity of a global industry got them to you? (We can ask the same thing of so many of our possessions, which have terrible secrets at their heart.)

Individual mussels can live a century, but nothing on earth can stand the might of the human machine. The life-cycle of these freshwaters is rather interesting: the larvae attach themselves to fish and hence spread along river systems. The most common species, Elliptio complanata, attaches itself to eels. In rivers that have been heavily dammed, like the Susquehanna, both eels and E.complanata have been largely obliterated. The Delaware, which is undammed, has an estimated two million mussels per mile, filtering two billion gallons of water per mile per day, central to a complex web of life connecting the air, water, and land.