Meeting Abstract

P3.176  Tuesday, Jan. 6  Elastic energy storage and the mantis shrimps powerful predatory strike ZACK, T/I; CLAVERIE, T; PATEK, S/N*; Univ. of California, Berkeley; Univ. of California, Berkeley; Univ. of California, Berkeley zacktravis@gmail.com

Storage of elastic energy is key to increasing the power output of jumping and predatory strikes. One notable example is the energy stored prior to the extremely rapid raptorial strikes in mantis shrimp (Stomatopoda). Several structures have been proposed as the site of elastic energy storage, including a leaf-spring shaped structure (meral-V) and a saddle-shaped structure (saddle) located on the lateral and dorsal sides of the merus segment of the raptorial appendage, respectively. The goals of this study were to determine the location of elastic energy storage, characterize the elastic behavior, and to examine the scaling of energy storage across a range of body sizes. Using a materials testing apparatus, we directly measured the force and work required to contract the elastic structures in 25 Gonodactylus falcatus individuals. We found that the force needed to contract the appendage exhibits a positive and linear correlation with the distance it has been contracted. Thus, this system can be modeled as a simple Hookean spring with a spring constant of 58.3 N.mm^-1 ( 10.6). The overall force required to compress the spring is positively correlated with body length and appendage size, but the spring constant is not correlated with body size. The primary site of elastic energy storage is in the meral-V rather than the saddle. However, removal of the saddle causes the system to exhibit greater fatigue and dramatically increased the probability of failure. In conclusion, the meral-V provides the elastic energy storage to power the strike, and the saddle most likely confers dynamic stability. Uniformity of the spring constant suggests that larger individuals simply compress a similar spring over greater distances to power their larger appendages.