Meeting Abstract

P1.164  Sunday, Jan. 4  It’s tough to be small: Dependence of burrowing kinematics on body size CHE, JAMES*; DORGAN, KELLY M; University of California, Berkeley; University of California, Berkeley jche@berkeley.edu

In marine muds, the polychaete Nereis virens burrows by the method of crack propagation, which involves the extension of a crevasse rather than ingestion or excavation of sediment. In gels with different material properties, Nereis virens alters its burrowing behavior as predicted by fracture mechanics theory. Observations of the marine worm Cirriformia moorei agree with this wedge-like model of locomotion. My experiments involved video analysis of worms ranging from 0.01 to 0.44 g wet weight burrowing in gelatin, a transparent analog for muddy sediment. Following predictions from fracture mechanics theory, several behavioral and kinematic parameters correlate with body size. When propagating the crack, smaller worms have blunter head tips, thicker (relative to body size) anterior regions, and a greater relative change in body thicknesses (amplitude of peristaltic wave). Smaller worms tended to contort their hydrostatic bodies more than larger worms in order to focus enough stress at the crack tip to extend the burrow. These behavioral differences may increase the relative contribution to bioturbation by smaller worms.