Taylor, J.R.A. and S.N. Patek. 2010. Ritualized fighting and biological armor: the impact mechanics of the mantis shrimp’s telson. Journal of Experimental Biology 213: 3496-3504.
Journal of Experimental Biology
Resisting impact and avoiding injury are central to survival in situations ranging from the abiotic forces of crashing waves to biotic collisions with aggressive conspecifics. While impacts and collisions in biology are ubiquitous, most studies focus on the material properties of biological structures under static loading. Here we examine the mechanical impact properties of the mantis shrimp’s telson, a piece of abdominal armor that withstands repeated, intense impacts from the potent hammer-like appendages used by conspecifics during ritualized fighting. We measured the coefficient of restitution, an index of elasticity, of the telson and compared it to an adjacent abdominal segment that is not impacted. We found that the telson behaves more like an inelastic punching bag than an elastic trampoline, dissipating 69% of the impact energy. Furthermore, while the abdominal segment provides no mechanical correlates with size, the telson’s coefficient of restitution, displacement and impact duration all correlate with body size. The telson’s mineralization patterns were determined through micro-CT (Computed Tomography) and correspond to the mechanical behavior of the telson during impact. The mineralized central region of the telson “punched” inward during an impact while the surrounding areas provided elasticity due to their reduced mineralization. Thus, the telson effectively dissipates impact energy while potentially providing the size-related information critical to its role in conspecific assessment. This study reveals the mechanical infrastructure of impact resistance in biological armor while also opening a new window to the biomechanical underpinnings of animal behavior and assessment.