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A small mussel attached to a larger one using a bundle of adhesive threads, known as a byssus (red arrow). Credit: jkirkhart35, CC BY 2.0.
The “beards” of marine mussels aren’t just a fashion statement. They anchor the mussels to the sea floor, attach to each other to form large “beds,” and hold out potential invaders. They’re also playing a role in materials research—scientists study the beards to learn how to make water-proof glue for many applications.
The beards consist of a bundle of about 20 to 60 threads known as a byssus. The threads radiate outward from the mussel’s “foot.” Each thread is tipped with a biological superglue—a combination of proteins from the mussel and metals from the water.
Mussels use the byssus to anchor themselves to the bottom, where they wait for tiny prey organisms to float through their shells. The threads are strong but flexible, so they allow the mussels to sway with the tides. The glue never dissolves in the water. The mussels can use the threads to move along the bottom; they anchor one thread, then “reel” it in to shift position.
When the mussels are threatened, though, they let go in a hurry. Tiny hairlike structures on the bottom of the foot beat rapidly, detaching the byssus from the mussel’s body. The mussel grows a new one in just a few hours.
Scientists are studying the byssus to help develop ways to attach sensors or implants to the human body. They’re also looking for ways to overcome the glue to prevent mussels—especially freshwater species—from fouling underwater outlets or other structures—getting free of some “sticky” threads.
