title: Unique crystallographic pattern in the macro to atomic structure of Herdmania momus vateritic spicules.
abstract: Biogenic vaterite is extremely rare. The only known example of a completely vateritic mineralized structure is the spicule of the solitary ascidian, Herdmania momus. In characterizing the structure of these spicules, using state-of-the-art techniques such as synchrotron X-ray diffraction and synchrotron micro- and nanotomography, we observed a continuous structural pattern from the macro down to the micro, nano, and atomic scales. We show that the spicules demonstrate a unique architecture composed of micron-sized, hexagonally faceted thorns organized in partial spirals along the cylinder-like polycrystalline body of the spicule, and tilted from it at an angle of about 26°. This morphological orientation coincides with the crystallographic orientation relationship between each thorn and the polycrystals within the spicule. Hence the entire spicule grows along the [011] direction of vaterite while the individual thorns grow along the [001] direction. This, together with the presence of both inter- and intra-crystalline organic phases, beautifully displays the organism's ability to achieve perfect control of mineralization biologically while employing an unstable polymorph of calcium carbonate: vaterite.
authors.affiliation: Department of Materials Science and Engineering, Technion - Israel Institute of Technology, 32000 Haifa, Israel.
authors.forename: Lee
authors.initials: L
authors.lastname: Kabalah-Amitai
authors.forename: Boaz
authors.initials: B
authors.lastname: Mayzel
authors.forename: Paul
authors.initials: P
authors.lastname: Zaslansky
authors.forename: Yaron
authors.initials: Y
authors.lastname: Kauffmann
authors.forename: Peter
authors.initials: P
authors.lastname: Clotens
authors.forename: Boaz
authors.initials: B
authors.lastname: Pokroy
mesh_terms: D060105:Animal Shells / Q000033:anatomy & histology / Q000254:growth & development* / Q000378:metabolism; D000818:Animals; D002119:Calcium Carbonate / Q000737:chemistry; D003461:Crystallography; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D014561:Urochordata / Q000033:anatomy & histology* / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D002119:Calcium Carbonate
keywords: Ascidians; BF; Biogenic crystals; Biomineralization; Crystallographic orientations; FIB; Focused Ion Beam; HRSEM; HRTEM; HV; High-resolution characterization techniques; SEM; TEM; Vaterite; bright field; high voltage; high-resolution scanning electron microscopy; high-resolution transmission electron microscopy; scanning electron microscopy; transmission electron microscopy