Echinoderms: Hierarchically Organized Light Weight Skeletons

Echinoderm skeletons are described within a hierarchical framework ranging from complete organisms to the ultrastructural level. They consist of numerous elements which can be isolated, connected by soft tissue or locked together in rigid structures. The top level considers skeletons as a whole with all associated elements and the basic symmetry of the echinoderms. The next level deals with the structural analysis and modeling of echinoids with respect to the growth parameters and stress resistance of the corona. The flexibility and movement has also been studied for the stalks and arms of recent and fossil crinoids. The next level deals with the elaborate morphology and types of symmetry found in single skeletal elements. The numerous types of stereom architectures found within the elements of all echinoderms are highly correlated to specific functions. A high number of recent studies concern the last hierarchical level on ultrastructure and biomineralization. Lightweight aspects of the skeleton are especially present at the level of conjoined plates, single elements and the stereom