Common crystallographic control in calcite biomineralization of bivalved shells

Abstract

The knowledge of how mineral-producing organisms exert precise control on their crystallographic orientation is one of the most fundamental questions of biomineralization. We demonstrate that organisms that construct bivalved shells have common mechanisms of controlling the crystallographic orientation of calcite biominerals despite their different evolutionary history. Detailed crystallography in the context of shell ultrastructure in rhynchonelliform brachiopods and bivalve molluscs indicates that at the umbonal regions calcite crystals are oriented with the c-axis <0001> nearly parallel to the shell surface and progressively rotate during growth. Such detailed contextual crystallography of biomineralization, using electron backscatter diffraction (EBSD), will have significant applications for future research in materials, biological and medical sciences.