Tailored disorder in calcite organization in tergite cuticle of the supralittoral isopod Tylos europaeus Arcangeli, 1938

In this study, we investigate structure, chemical composition, mineral organization and local mechanical properties of the anterior and posterior edges of the tergite cuticle in the conglobating beach isopod Tylos europaeus and compare these with the protective dorsal region of the tergites.The distribution of mineral phases at the edges resembles that of dorsal regions of the tergites. At the transition with the unmineralized arthrodial membrane the calcite containing distal exocuticle is replaced by epicuticular material and the subjacent cuticular layers containing amorphous calcium carbonate become enriched with amorphous calcium phosphate. At the edges, the local elastic modulus and hardness values are significantly lower compared to dorsal regions of the tergite cuticle, for both, the calcite and the amorphous mineral containing layers. The calcite within the tergite cuticle is assembled in different texture patterns: (i) almost random co-orientation, (ii) almost single crystalline calcite, and (iii) a graded organization. Calcite organization and co-orientation strength is highly variable, not only on very few tens of micrometres, but also between regions with different skeletal functionality. Our results show that besides structure and composition, patterns of calcite organization contribute to the hierarchical architecture and functionality of biological composites.Graphical abstract
Source: Journal of Structural Biology - Category: Biology Source Type: research