Close up of the bridges that connect sea urchin teeth.
Image courtesy of Pupa Gilbert, University of Wisconsin-Madison (2011)
Sea urchin teeth have many plates of crystalline calcite. The details of the connections between the plates had never been identified. This scanning electron microscope image shows the recently discovered calcite mineral bridges that connect the developing tooth plates in the sea urchin Eucidaris tribuloides. The bridges are later reabsorbed before the tooth emerges. Their formation mechanisms fascinate physicists, materials scientists, and chemists because they result in materials that are stronger than their components, with exquisitely intricate nano-structures, that are able to fill more space and control transitions.