Zebra Mussel

Family: 
Dreissenidae (a group of freshwater mussels) in the phylum Mollusca
Description: 

The shells of these mussels are triangular, with alternating light and dark bands and a prominent ridge. A concavity about midway allows the animal inside to secrete byssal (holdfast) threads, permitting the mussel to attach itself to almost any solid substrate. In areas infested with zebra mussels, they often clump together, covering rock, metal, rubber, wood, docks, boat hulls, native mussels, crayfish and even aquatic plants.

Size: 
Adult length: ¼-1 inch.
Habitat and conservation: 
Native to the Caspian Sea region of Asia, these mollusks were accidentally introduced to North America in 1986 from ballast water of an international ship. They have tremendous reproductive capabilities and have a huge negative impact on the waters they infest. They have spread rapidly throughout the Great Lakes, the Mississippi, Arkansas, Ohio, Tennessee and Cumberland rivers. No one has found a way to stop their spread, so the only thing to do is take steps not to spread them any further.
Foods: 
Zebra mussels filter plankton from water. Each mussel can filter about a quart of water per day. But not all of what they remove is eaten. What they don't eat is combined with mucus as "pseudo-feces" and discharged onto the lake bottom where it accumulates. This material, which may benefit bottom feeders, also may reduce the plankton food chain for upper water species.
Distribution in Missouri: 
Found in the Mississippi River, the Missouri River near Sioux City, Iowa, and in the lower Meramec. Its range is spreading.
Status: 
An invasive exotic organism. Overland transport on boats, motors, trailers and aquatic plants poses a great risk for spreading them. Adult zebra mussels can live several days out of water. Boats that have been moored or stored even a day or two in zebra mussel-infested waters may carry "hitchhiking" mussels attached to their hulls, engine drive units and anchor chains. Microscopic zebra mussel velgers can survive in bilge water, livewells, bait buckets and engine cooling water systems.
Life cycle: 
Female zebra mussels can produce as many as 1 million eggs per year. These develop into microscopic free-swimming larvae (veligers) that quickly begin to form shells. At about three weeks, the sand-grain-sized larvae start to settle; by secreting tough byssal threads, they attach to any firm surface. They clump together and cover just about any surface available. They commonly reach a density of 30,000–40,000 individuals per square meter.
Human connections: 
Zebra mussels can clog power plants, industrial and public drinking water intakes, foul boat hulls and impact fisheries. Economic impacts of zebra mussels in North America during the next decade are expected to be in the billions of dollars.
Ecosystem connections: 
Zebra mussels have a tremendous negative impact on aquatic ecosystems, changing the quality of the water, outcompeting native freshwater mussels, and reducing the plankton available that form the basis for fish life.