Figure 1.

M. californianus byssus. (a) Mussel byssus mediates modulus mismatch between the hard substrate and soft tissue in the high-energy intertidal zone, where mussels are threatened with dislodgement by lift, drag, and abrasion. (b) Transmission electron micrograph of a longitudinal cross-section [zoom-in of the boxed area in panel a] of the thread core and cuticle. As the outermost covering of the byssus, the cuticle serves as a vanguard of resistance to three major types of frictionally induced damage. Site 1: sand-cuticle frictional damage. Site 2: core-cuticle frictional damage. Site 3: granule-matrix frictional damage.