They were accidentally introduced to North America in ballast water from a boat that traveled across the ocean. Zebra mussels come in many colors. Most are white or cream-colored with jagged brown or black stripes. Mollusca comes from the Latin word, mollis, meaning soft. Slugs, snails, octopuses, clams, and oysters are all mollusks.
Mussels are bivalve mollusks.
Bivalves have two shells that are held together by a strong ligament. Female zebras release a cloud of eggs. They feed on tiny phytoplankton and begin to grow shells. The water currents can cause veligers to travel great distances. At 3 - 4 weeks, the veligers' shells weigh enough to cause them to sink.