The spines of an urchin’s exoskeleton are formed by a hollow single crystal calcite, with an intricate pattern that makes the spines strong and flexible despite their brittleness.

Engineers created a 3D model of the spine’s structure using microtomography (3D x-ray scanning) to understand more about the spine’s flexibility and load bearing properties.

Urchins use the spines for walking and sensing their environment, as well as protection from impacts. The brittleness of the spines allows them to break off when the urchin is attacked by predators.