Investigating how Morphological Change Alters the Competing Demands of a Biological Spring

Michael Rosario, University of Massachusetts, Amherst

Although the use of elastic mechanisms in animal locomotion is widespread in nature, few studies compare these mechanisms to understand the universal principles that affect energy storage and power amplification. In this study we address whether or not the morphology of elastic mechanisms can balance the competing demands of deformation during energy storage and prevention of failure due to excessive stress. In order to answer this question, we created finite element (FE) models from micro computed tomography scans of the appendages of mantis shrimp. These crustaceans utilize elastic storage to generate strikes with over 500 N of force and with accelerations over 100 km/s^2. We investigate the role of the saddle, a hyperbolic paraboloid portion of the exoskeleton within the mantis shrimp appendage, on strain energy density and stress by analyzing each FE model with and without the saddle present. We also developed a visualization tool in the R statistical environment to help us qualitatively assess the results of our study in an interactive 3-D plot. Our models predict that the morphology and location of the saddle reduce the concentration of stress throughout the appendage during static loading and that the saddle concentrates energy in the elastic mechanism of the appendage in species that rely heavily on power amplification. This suggests that the shape and location of the same structure in different species may be adjusted to alter functionality and still meet the demands of the elastic mechanism.

Abstract Author(s): Michael Rosario, Elizabeth Dumont, Sheila Patek