The ability to strongly attach to both man-made and natural structures is unique to the dreissenids. Attachment is accomplished by strong cords or byssal threads that arise from the bottom or ventral portion of the organism.
Note: The byssal threads may get pulled out while removing the mussel from the substrate. Keep this in mind when identifying the mussel.
Zebra mussels attach to a variety of surfaces with the use of strong, elastic byssal threads. The ability to strongly attach to both man-made and natural structures is unique to the dreissenids. Note how the byssal threads are located at the bottom or ventral portion of the organism.
For further information see Bottom Shape.