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The extensible byssal threads of marine mussels consist of an outer cuticle and inner collagen core. These threads display notable tensile mechanics. They maintain these resilient properties through the repeating stress applied to them by the wave swept environment that they occupy, showing hysteretic straining and recovery of stiffness. There is much we can learn from the complex stress dissipation network that the mussel has evolved to survive in its environment, which we can translate to synthetic systems. The relative contributions of the core and the cuticle to the overall mechanics are unknown. My current research will investigate each components influence by measuring strain to failure tests using an MTS tensiometer on distal thread sections of Mytilus californianus (an common local intertidal variant) that have been treated with pepsin and collagenase (pepsin selectively degrades the cuticle, whereas collagenase selectively degrades the core) in order to isolate the mechanical behaviour of different sections. Information on the characteristics of the cuticle has been gleamed from the results. Moreover, I hope to identify causes of compliance differences between threads of a single mussel and the interplay of amorphous and crystalline regions of the proteinaceous mussel byssus. Initial testing suggests that the collagen core of the thread is overwhelmingly responsible for the mechanical behaviour of the byssal thread. However, further investigation is needed to clarify ascertain the purpose of the thread cuticle.