Most people are relatively familiar with blue mussels (Mytilus edulis), even if only from a menu at a seafood restaurant. This popular edible bivalve (a shellfish with a hinged pair of shells) is circumpolar in its range, and in the western Atlantic Ocean extends as far south as South Carolina. Unlike the ribbed mussel that is commonly found in salt marshes and brackish water areas, the blue mussel is more common along rocky saltwater shorelines. 

These rocky areas in which blue mussels often live tend to be areas with relatively high wave energies. If you’ve ever been in the ocean on a day with even minor surf, you’ve experienced how powerful the waves can be. Now imagine how tossed around you would be if you were only a few inches long like a mussel. In order to remain in place, and not get washed away from an ideal feeding area or smashed onto nearby rocks, blue mussels have evolved a unique adaptation to anchor themselves in place: byssal threads. These byssal threads are formed when a special liquid is secreted by a gland located near the mussel’s foot. Each liquid “thread” hardens upon contact with water, helping to hold them onto rocks, structures, or whatever else is available. Byssal threads are strong and waterproof – properties that make this material of high interest to materials scientists.

Not only do these byssal threads hold the mussels securely to hard substrates, but they can also hold the mussels to each other, to smaller stones and pebbles, or whatever is nearby (see photo above which shows some small snail shells also wrapped up in the tangle of byssal threads). When this happens, large aggregations of mussels can form dense mussel beds or mussel reefs. The reefs can help attenuate wave action, reduce erosion, and provide an ample food source for wildlife. Mussel beds like the one pictured here form a veritable buffet for gulls, eiders, and other sea birds. Turns out humans aren’t the only ones that think mussels are delicious.