UC Berkeley

Dermal armor is responsible for the protection of many species, although it comes at the expense of mobility due to added weight and rigidity. In fish, it is especially effective because it enhances protection from predator teeth without markedly sacrificing mobility or affecting buoyancy. Elasmoid scales, in particular, have evolved to create a major defense strategy. The scales overlap and have individual flexibility, and so do not hamper the mobility of the fish. We have defined the structure of carp scales at multiple structural levels and compare them with other previously studied elasmoid scales, e.g., the arapaima and coelacanth. Akin to these scales, carp scales display a “twisted plywood” structure consisting of lamellae of collagen fibrils with different orientations, which provides resistance to damage through a synergy of deformation mechanisms, including collagen fiber stretching, rotation, sliding, and delamination, all of which serve to maintain the integrity of the scale.