SICB Division of Invertebrate Zoology (DIZ)

DIZ Researchers Database Entry

Kelly Dorgan

Nereis virens burrowing in gelatin by crack propagation
This photograph was taken with circularly polarized light and shows the stress field around a burrowing polychaete. Gelatin has similar mechanical properties (critical stress intensity factor and Young's modulus) to muddy sediments and is birefringent, enabling use of photoelastic stress analysis. Stress fields re-orient the light, enabling it to pass through crossed polarizers. We show that Nereis burrows by crack propagation, with the dual anchor system serving instead to exert a normal force against the burrow wall. This force is intensified at the crack tip, causing the crack to propagate and the burrow to extend. The crack tip is visible extending anterior of the worm.