Calcite Reinforced Silica-Silica Joints in the Biocomposite Skeleton of Deep-Sea Glass Sponges

• Published in: Advanced functional materials 2011-09, Vol.21 (18), p.3473-3481
• Main Authors: Ehrlich, Hermann, Brunner, Eike, Simon, Paul, Bazhenov, Vasily V., Botting, Joseph P., Tabachnick, Kontantin R., Springer, Armin, Kummer, Kurt, Vyalikh, Denis V., Molodtsov, Serguei L., Kurek, Denis, Kammer, Martin, Born, René, Kovalev, Alexander, Gorb, Stanislav N., Koutsoukos, Petros G., Summers, Adam
• Format: Article
• Language: English
• Subjects: biomineralization; Calcite; composite materials; Glass; hierarchical Structures; Low concentrations; Secretions; silica; Silicon dioxide; Spicules; Sponges; Surgical implants
• ISSN: 1616-301X; 1616-3028; 1616-3028
• DOI: 10.1002/adfm.201100749

The hierarchically structured glass sponge Caulophacus species uses the first known example of a silica and calcite biocomposite to join the spicules of its skeleton together. In the stalk and body skeleton of this poorly known deep‐sea glass sponge siliceous spicules are modified by the addition of conical calcite seeds, which then form the basis for further silica secretion to form a spinose region. Spinose regions on adjacent spicules are then joined by siliceous crosslinks, leading to unusually strong cross‐spicule linkages. In addition to the biomaterials implications it is now clear, from this first record of a biomineral other than silica, that the hexactinellid sponges are capable of synthesizing calcite, the ancestral skeletal material. We propose that, while the low concentrations of calcium in deep sea waters drove the evolution of silica skeletons, the brittleness of silica has led to retention of the more resilient calcite in very low concentrations at the skeletal joints. In the stalk and body skeleton of deep‐sea glass sponge Caulophacus species siliceous spicules are modified by the addition of conical calcite seeds, which form the basis for further silica secretion to form a spinose region. The hierarchically structured glass sponge uses a silica and calcite biocomposite to join the spicules of its skeleton together, and the hexactinellid sponges are capable of synthesizing calcite, the ancestral skeletal material. Computer reconstruction is based on scanning electron microscopy images and represents the view on mechanical coupling between unique spinose surfaces of two thin spicules within one large spicule.