See text Dreissena is a genus of small freshwater mussels in the family Dreissenidae in the class Bivalvia.

They are found attached to firm substrates by threads from underneath the shells and are the only freshwater bivalves to attach to hard substrates in high densities while having a planktonic larval stage.

The outer covering is a well polished light tan color with dark bands that can either be smooth or zigzagging in shape.

Originally found in Ukraine and Southeast Russia but have spread worldwide via ballast water and on the hull of boats, and are now in North America in the Great Lakes.

They prefer large estuaries and inland waters, rivers and lakes, and require firm surfaces for attachments.

Eggs are expelled by females in their second year of life and are fertilized outside of the body by males.

The invasion of North America was facilitated by the ability to disperse in all stages of the life cycle: passive drift of pelagic larval, yearlings detach and drift, adults attach to boat hulls and other floating objects.