Mussels attach themselves to the hard surfaces using their thread-like byssus. The animals attach themselves to a solid substrate using a byssus. Some attach to the substrate using a byssus. It attaches itself to rocks or other hard substrates in shallow water with byssus threads. Blue mussels often form aggregations, where they attach to each other using byssus threads. It prefers soft substrates and surrounds its shell in a dense mass of byssus. Other paired muscles control the siphons and the byssus. This means that the name "Hypochnus rubrocinctum" has priority over "Byssus sanguinea". Most species lose the byssus as they grow larger. The pearl oyster attaches itself to barnacles and other hard substrates via a byssus. It is attached by byssus threads when young but may be detached when older. They attach themselves to stones or to any other hard surface using a byssus. The ligament and byssus, if calcified, are composed of aragonite. The byssus is used by the clam to attach itself to the sea bed. It also produce byssus to help it attach to its substrate.