Mussels attach themselves to hard substratum with the help of byssal threads from the byssal glands. These proteinous threads are very strong, a defense mechanism for the mussel. Many mussels attach themselves to rocks that are in the intertidal region; therefore, they are under a lot of physical stress from possible dessication, wave action, exposure to ariel prey, as well as competition for space with barnacles, algae, and other mussels.
