Meeting Abstract
84.2 Thursday, Jan. 7 Shape, size and performance of a crustacean predatory appendage CLAVERIE, T.*; CHAN, E.K.; PATEK, S.N.; Univ. of Massachusetts, Amherst; Univ. of California, Berkeley; Univ. of Massachusetts, Amherst tclaverie@gmail.com
While variation in size can be intuitively linked to performance, the role of shape in the development and evolutionary radiations of predatory structures is rarely studied. Here we examine correlates of shape, size and performance in the mantis shrimp, Gonodactylaceus falcatus (Crustacea: Stomatopoda). Mantis shrimp raptorial appendages are powered by springs, four bar linkages, and levers that work in concert to amplify rotation during predatory strikes. We applied geometric morphometric techniques and selected the appropriate recording methods and landmarks across a size range of individuals. We digitized 2D landmarks and semi-landmarks on the raptorial appendages of 56 individuals. Then, size was measured using traditional linear morphometrics. We used a published dataset of spring constants and spring forces from these individuals and also collected force data from these same specimens using piezoelectronic impact sensors. We found that females had relatively smaller appendages than males, appendages were left-right symmetric in both sexes, and subtle shape variations were correlated with size and sex. Spring force and strike force were positively correlated with body size, but not shape. The spring constant was correlated neither with shape nor size. Shape variation in the merus segment (housing the spring and linkage systems) was independent of the covariation observed between the propodus and dactylus segments (acting as levers and striking surfaces). While size provides the most explanatory power for performance differences, the independent variation of shape in the two functional regions of the raptorial appendages may indicate developmental modularity and could underlie the extraordinary diversity of these appendages across the 500+ mantis shrimp species.
