Strong black coral: high-energy phase contrast tomography for visualizing the internal crack stopping mechanisms of a non-mineralized coral

The black coral antipatharians Stichopathes sp. live in a range of habitats of extreme depths in different seas worldwide. They form coiled wires, that are poorly mineralized yet they posses a hard and extremely damage resilient chitin-based skeleton that is largely unexplored. The coral exhibits extraordinary toughness making it very difficult to break, presumably needed for life in the harsh habitat. We propose to study the relation between chitin fibers, cavities and internal architecture and forces needed to deform and fracture the coral, measured by in-situ 3 point bending on ID19, to be able to image the tension and compression sides of specimens exposed to increasing loads. With energies above 75 keV we will avoid radiation damage and directly visualize internal damage arresting structures at micrometer resolution. This will shed light on damage resistant mechanisms that evolved under environmental conditions that are very different than those found on land.