Sipunculid burrows in coral reefs: Evidence for chemical and mechanical excavations

The crystalline structure of sipunculid burrow linings from dead coral as studied with the scanning electron microscope indicates the presence of etching similar to that produced by treatment of unmodified coral surfaces with acid, and with EDTA. Initial biochemical activity appears to weaken intercrystalline bonds, permitting detachment of crystals by mechanical abrasion and subsequent deposition of their fragments in spaces between corallite walls.