Meeting Abstract
The skin of non-tetrapod fishes provides several important functions, including protection from the external environment, water balance, and gas exchange. The role skin plays in biomechanical systems such as locomotion and feeding has received little attention by scientists. With its cross-helical arrangement of collagen fibers, fish skin may contribute to swimming by maintaining hydrodynamic body shape and serve as a lateral tendon that increases the mechanical advantage of the body musculature and stores elastic energy. The material properties of fish skin that underlie these functions have been explored in detail in only a few species of sharks, an eel, and a limited number of percomorph fishes. In this study, we tested uniaxial, longitudinal stiffness along the entire trunk of three species of teleost fishes—a salmon, lutjanid snapper, and pompano. We also undertook uniaxial testing of the hyoid skin form our lutjanid snapper species. Based on over 300 strain experiments, we found that uniaxial stiffness increases along the anterior-posterior axis of the trunk in all three species. Skin from the trunk of the snapper skin was only approximately 5 times as as stiff as skin from the hyoid region. We also found that trunk skin stiffness varies considerably between species with pompano having the stiffest skin, 60 times more stiff than sockeye salmon, the least stiff of our study species. Combined, our findings of a stiffness gradient along the trunk and that fishes with faster swimming performance have much stiffer skin indicate that skin plays an important role in transmitting force during body-caudal fin propulsion. The dramatic differences in skin stiffness between skin samples from feeding and locomotor systems also suggest that skin material properties can be tuned to specific performance and behavioral goals.
