What is the difference between a native mussel and the zebra mussels?
A. Native mussels are in a group, or family called “Unionidae”. In general, unionids are much larger than the zebra mussels. Unionids have a larval stage, called a “glochidia” (which rhymes with the name “Lydia”). The glochidia must attach to the gills or fins of a fish to transform (or “metamorphose”) into juvenile clams. Zebra mussels (scientific name Dreissena polymorpha) were probably introduced into Lake St. Clair in 1986, most likely from the ballast water of a Great Lakes ship. A single female of a unionid mussel and a zebra mussel can produce several thousand eggs per year. However, zebra mussels don’t have a parasitic stage. Since they don’t need this extra step to become adults, populations are able to grow and survive at a greater rate than the native mussels. Q: Do the glochidia harm the fish? A: Not really. There are a few records of fish in a hatchery being harmed, but this was under unnatural conditions. The glochidia may actually help the fish develop an immunity to oth
