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Where Did Zebra Mussels Come from?

Zebra mussels, Dreissena polymorpha, are small bivalve organisms with a characteristic black and white striped pattern on their shells. According to the University of Wisconsin Sea Grant Institute, these fresh water creatures seldom get bigger than about 1 and 1/2 inches in length. Originally found in Russian waters, zebra mussels are not native to North America, and with no natural predators, they are considered an invasive species.

Origins
- The Zebra Mussel Information System (ZMIS) of the U.S. Army Corps of Engineers states that the zebra mussel first was described in 1771 by Russian explorer Pyotr Simon Pallas, who described a population of them he found in a tributary of the Ural River. According to ZMIS, boat traffic from Russia spread the species throughout Europe by the 19th century.
Arrival in North America
- In 1988, zebra mussels were noticed for the first time in North American waters. The 100th Meridian Initiative website states that they were found in Lake St. Clair, near Detroit, Michigan, which connects Lake Erie with Lake Huron. ZMIS describes the mussels as being 2 to 3 years old at the time and conjectures that the mussels may have been transported as larvae, juveniles and adults in the fresh-water ballast of ships that had traveled from Europe across the Atlantic Ocean.
Spread
- Since 1988, zebra mussels have spread throughout freshwater systems from the Great Lakes all the way to the Gulf of Mexico. The 100th Meridian Initiative states that they are found in the Mississippi River drainage system as well as the Arkansas River and the Colorado River. By 1999 they had been recorded in 21 U.S. states.
Methods of Dispersal
- In addition to dispersal by boats, zebra mussels that are attached to aquatic plants or animals may be spread by these organisms. Free-floating larvae travel downstream as well, according to ZMIS.

Insects & Science