Meeting Abstract

84.4  Thursday, Jan. 7  Biological punching bags: impact analysis of a mantis shrimp telson TAYLOR, Jennifer R. A.*; PATEK, Sheila N.; Univ. of California, Berkeley; Univ. of Massachusetts, Amherst jrataylor@berkeley.edu

Collisions are prolific in nature and can impart significant impact forces on organisms. Our understanding of how biological structures respond to impact forces is limited, partly because most studies on material properties are conducted under static or quasi-static loading conditions. Here we perform an impact analysis on one of nature’s remarkable punching bags: the mantis shrimp telson. During ritualized fighting, mantis shrimp (Crustacea, Stomatopoda) repeatedly strike each other with their raptorial appendage, delivering extremely fast and powerful blows to the telson of the opponent. Hence, the telson may respond differently to impact than other body regions, e.g. the abdomen. To test this, we performed ball drop tests on 16 Neogonodactylus wennerae that ranged from 0.47 to 4.6 g body mass. Small steel balls were dropped onto the telson and abdomen and recorded using high speed videography. Velocities were calculated from the video frames and used to determine the coefficient of restitution (COR), an index of elasticity (lower values mean less elasticity). The telson COR (0.56) was significantly lower than the abdomen COR (0.66), meaning that the telson absorbs 10% more impact energy than the abdomen. The telson COR was negatively correlated with body mass, while the abdomen COR showed no correlation. There was no difference in the COR for males and females. These results show variation in the impact response of morphologically different body structures. The telson, much like a punching bag, withstands and absorbs the impact of repeated blows, but the mechanism of energy absorption has yet to be explored. The impact response of the telson may be an integral component of assessment during ritualized fighting, and thus important in the evolution of telson morphology.