title: Microstructure and crystallographic-texture of giant barnacle (Austromegabalanus psittacus) shell.
abstract: Barnacle shell is a very complex and strong composite bioceramic composed of different structural units which consist of calcite 15 microcrystals of very uniform size. In the study reported herein, the microstructural organization of these units has been examinated in detail with optical and scanning electron microscopy, and X-ray diffraction techniques. These analyses showed that the external part of the shell has a massive microstructure consisting of randomly oriented crystals. Toward the interior, the shell became organized in mineral layers separated by thin organic sheets. Each of these mineral layers has a massive microstructure constituted by highly oriented calcite microcrystals with their c-axes aligned [(001) fibre texture] perpendicular to the organic sheets and the shell surface. Interestingly, in another structural unit, the shell shield, the orientation of the c-axis calcite crystals shifts from being perpendicular to being parallel to the shell surface across its thickness. This study provides evidence that the organic matrix is responsible for the organization of the shell mineral and exterts strong a strict control on the polymorphic type, size and orientation of shell-forming crystals.
authors.affiliation: Departamento de Mineralogía y Petrología, Universidad de Granada, Spain. anava@ugr.es
authors.forename: Alejandro B
authors.initials: AB
authors.lastname: Rodríguez-Navarro
authors.forename: Christiane
authors.initials: C
authors.lastname: CabraldeMelo
authors.forename: Nelson
authors.initials: N
authors.lastname: Batista
authors.forename: Nilton
authors.initials: N
authors.lastname: Morimoto
authors.forename: Pedro
authors.initials: P
authors.lastname: Alvarez-Lloret
authors.forename: Miguel
authors.initials: M
authors.lastname: Ortega-Huertas
authors.forename: Victor M
authors.initials: VM
authors.lastname: Fuenzalida
authors.forename: Jose I
authors.initials: JI
authors.lastname: Arias
authors.forename: Juan P
authors.initials: JP
authors.lastname: Wiff
authors.forename: Jose L
authors.initials: JL
authors.lastname: Arias
mesh_terms: D000818:Animals; D003460:Crystallization; D003461:Crystallography / Q000379:methods*; D008954:Models, Biological; D001468:Thoracica / Q000737:chemistry* / Q000648:ultrastructure*; D014961:X-Ray Diffraction / Q000379:methods