Coexistence of Amorphous and Crystalline Calcium Carbonate in Skeletal Tissues

• Published in: Connective tissue research Vol. 44; no. 1; pp. 20 - 25
• Main Authors: Aizenberg, J., Weiner, S., Addadi, L.
• Format: Journal Article
• Language: English
• Published: England Informa UK Ltd 2003; Taylor & Francis
• Subjects: Amino Acids - analysis; Amorphous Calcium Carbonate; Animals; Ascidians; Biomineralization; Calcareous Sponges; Calcification, Physiologic - physiology; Calcite; Calcium Carbonate - chemistry; Calcium Carbonate - metabolism; Crystallization; Crystallography, X-Ray; Extracellular Matrix Proteins - chemistry; Extracellular Matrix Proteins - physiology; Microscopy, Electron; Porifera - physiology; Spectrophotometry, Infrared; Urochordata - physiology; X-Ray Diffraction
• ISSN: 0300-8207; 1607-8438
• DOI: 10.1080/03008200390152034

We describe a new type of composite skeletal tissues in which calcite and stabilized amorphous calcium carbonate (ACC) coexist in well-defined domains. The organisms that form such structures are widely separated in the animal kingdom phylogenetic tree: calcareous sponges and ascidians. This paper compares the microstructures of their composite skeletal elements: The triradiate spicules from the sponge Clathrina are composed of a core of calcite embedded in a thick layer of ACC and covered by a thin calcitic envelope; the tunic spicules from the ascidian Pyura pachydermatina are composed of a core of ACC enveloped by an insoluble organic sheath and covered by a thick calcitic layer. We compare and contrast the macromolecules associated with different amorphous and crystalline phases and their ability to induce the formation of stabilized ACC in vitro.