Meeting Abstract

S1-1.3  Jan. 4  Burrowing in muddy sediment by crack propagation DORGAN, K.M.*; JUMARS, P.A.; ARWADE, S.; University of Maine; University of Maine; Johns Hopkins University

Marine muds are elastic solids through which animals move by propagating a crack-shaped burrow. Dilations previously considered anchors serve to exert radial compressive stress that, through elastic behavior of the medium, focuses axial tensile stresses strongly at the tip of the burrow. This focused stress breaks adhesive bonds, propagating a crack for the animal to follow. The force required to propagate a crack by the polychaete Nereis virens has been measured in gelatin, an analogue of muddy sediment, using photoelastic stress analysis. Numerical modeling confirms experimental observations in gelatin and is used to determine the effect of differences in mechanical properties between sediment and gelatin. Newly calculated forces are lower than previously measured and call into question the reputed great expense of burrowing as a form of locomotion, although data on metabolic cost of transport are lacking.