Nanoengineering in echinoderms: The emergence of morphology from nanobricks

The stereom of echinoderms was investigated in order to understand their unique morphology and properties that seem impossible in single-crystalline materials. Spines of three species (Echinometra mathaei (Blainville), Anthocidaris crassispina (A. Agassiz), and Heterocentrotus mammillantus) and the shell of a sea urchin were used as samples. The nanoscopic structure on the fractured surface and in the powdered samples of all the specimens without any observation by FESEM or FETEM, respectively, was recognized. The stereom sample before NaClO treatment homogeneously incorporates the dye molecules. The growth of a calcitic skeleton in echinoderms is characteristic of the transition from amorphous calcium carbonate (ACC) to a single crystal.