Threads are secret to mussels' magical staying power

Fine dangling filaments give mussels an extraordinary ability to cling to rocks and ship hulls and survive the ocean's battering, scientists said on Tuesday. Mussels have long been feted for the glue with which they adhere to surfaces in the harsh marine environment -- a cement that chemists are trying to reproduce for industrial purposes. Just as remarkable, says a new study, is the web of the fragile-looking strands called byssus threads that the mussels use as an anchor chain. Unlike limpets, which clamp tightly on to a surface, the hair-like filaments enable the humble bivalve to hang on loosely. This gives it a tiny ability to drift, boosting its chances of tucking into micro-nutrients in the sea. But at the same time, dangling means the mussel gets sloshed about in the dynamic environment of crashing waves and currents. Glue alone cannot explain why the mussel is not bashed to pieces, said Markus Buehler, a professor of civil and environment engineering at the Massachusetts Institute of Technology (MIT). "We figured there must be something else going on. The adhesive is strong, but it's not sufficient," he said. He and MIT research scientist Zhao Qin analysed the byssus threads in a laboratory. They found that the fibres, secreted by a gland in the mussel, are a remarkable mixture of proteins. Eighty percent of each strand is of stiff material, which attaches to the surface with the help of the famous glue coating, while 20 percent is soft and stretchy, and adheres to the mussel. Put together, this mixture provides elasticity and rigidity, dampening the force of water but not fighting destructively against it. The mussel is able to withstand a dynamic loading -- the sloshing about -- that is nine times greater than a static loading, meaning when it is pulled in just one direction. The pair say that if the structure and chemistry of the byssus threads can be replicated, there are many outlets waiting for it, including anchorages for ships, submarines, wind turbines and spaceships. The study is published in the journal Nature Communications.