Meeting Abstract

82.3  Sunday, Jan. 6  Shrimp springs: how shape affects strength in energy storage ROSARIO, M.V.*; DUMONT, E.R.; PATEK, S.N.; UMass, Amherst; UMass, Amherst; UMass, Amherst mrosario@bio.umass.edu

Elastic systems are widespread in nature and vary in morphology across taxonomic groups. A key question in elastic systems is how shape influences strength, thereby affecting how much energy can be stored before failure. To address this question, we analyzed the spring system in the striking appendages of mantis shrimp (Stomatopoda). The fastest-striking mantis shrimp smash prey by using their springs to generate strikes exceeding 24 ms^-1. Shrimp that spear are less dependent on elastic energy and strike at slower speeds. First, we asked if cross-sectional shape of smasher appendages results in higher strength. Second, we tested how the location of the saddle (a major spring component) and its removal influence energy distribution in spearers and smashers. Shape factor analysis was used to analyze the effect of cross-sectional shape on bending strength. We also used finite element analysis and manipulations in silico to assess the effect of spring location and removal on strain energy density throughout the appendage. We found that smasher appendages achieve equivalent bending strengths as spearers while using less than 1/5 of the material. Removal of the saddle increases energy storage while variation in its position can decrease energy storage. We also found functional differences between smashers and spearers in the non-spring components of the appendages; the smasher configuration uniquely reduces energy in other regions of the appendage. These results suggest that species with higher dependence on fast, spring-loaded movements (i.e., smashers) may have cross-sectional shapes that increase spring strength, and that variation in the configuration of spring components affects the energy in regions other than the spring during spring compression.