Zebra Mussels Shine Brightly in Polarized Light

From June 5, 1992 (update #13)

GREEN BAY, Wis. - A technique used by geologists to examine the microstructure of crystalline rocks under cross-polarized light may prove useful to detect zebra mussel veligers in water samples. After learning of the technique from an article in New York Sea Grant's Dreissena polymorpha Information Review (Vol. 3, No. 1), Wisconsin Sea Grant's Zebra Mussel Watch Assistant Coordinator Jory Jonas tried the technique and found that preserved mussel veligers "glowed brightly against a dark background. Cross-polarization is accomplished by using a microscope with two polarizing filters - a tool commonly used by geologists - both above and below the sample. The technique involves rotating one filter until the only light passing through the microscope is that refracted by substances such as calcite and aragonite, which occur in the shells of larval mussels. Zebra mussel veligers are one of the few items in freshwater plankton samples that will appear iridescent under cross-polarized light. Further exploration of this technique is being undertaken by Ladd Johnson of Williams College, phone (313) 668-2571, and Ellen Marsden of the Illinois Natural History Survey, phone (708) 872-8676. To contact Jonas, call Sea Grant Advisory Services, UW-Green Bay, phone (414) 465-2798.

ID: 19920605-7.

The Zebra Mussel Update was a 4- to 8-page quarterly national newsletter published by the University of Wisconsin Sea Grant Institute from May 1990 through May 1997. The ZMU documented the spread of the zebra mussel -- an exotic nuisance mussel -- through North America's freshwater environments, especially the Great Lakes, and on efforts to control it.