title: Calcium Deposits in the Crayfish, Cherax quadricarinatus: Microstructure Versus Elemental Distribution.
abstract: The crayfish Cherax quadricarinatus stores calcium ions, easily mobilizable after molting, for calcifying parts of the new exoskeleton. They are chiefly stored as amorphous calcium carbonate (ACC) during each premolt in a pair of gastroliths synthesized in the stomach wall. How calcium carbonate is stabilized in the amorphous state in such a biocomposite remains speculative. The knowledge of the microstructure at the nanometer level obtained by field emission scanning electron microscopy and atomic force microscopy combined with scanning electron microscopy energy-dispersive X-ray spectroscopy, micro-Raman and X-ray absorption near edge structure spectroscopy gave relevant information on the elaboration of such an ACC-stabilized biomineral. We observed nanogranules distributed along chitin-protein fibers and the aggregation of granules in thin layers. AFM confirmed the nanolevel structure, showing granules probably surrounded by an organic layer and also revealing a second level of aggregation as described for other crystalline biominerals. Raman analyses showed the presence of ACC, amorphous calcium phosphate, and calcite. Elemental analyses confirmed the presence of elements like Fe, Na, Mg, P, and S. P and S are heterogeneously distributed. P is present in both the mineral and organic phases of gastroliths. S seems present as sulfate (probably as sulfated sugars), sulfonate, sulfite, and sulfoxide groups and, in a lesser extent, as sulfur-containing amino acids.
authors.affiliation: 1Sorbonne Universités,Biologie des Organismes et des Ecosystèmes Aquatiques (BOREA),UMR MNHN/CNRS-7208/UPMC/UCN/UA/IRD-207,Muséum National d'Histoire Naturelle,75005 Paris,France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Luquet
authors.affiliation: 2Sorbonne Universités,Département Systèmatique et Evolution,Mammifères et Oiseaux,Muséum National d'Histoire Naturelle,75005 Paris,France.
authors.forename: Yannicke
authors.initials: Y
authors.lastname: Dauphin
authors.affiliation: 3Sorbonne Universités,MONARIS, UMR 8233 CNRS/UPMC,Université Paris 06,75005 Paris,France.
authors.forename: Aline
authors.initials: A
authors.lastname: Percot
authors.affiliation: 4ID21, European Synchrotron Radiation Facility,38000 Grenoble,France.
authors.forename: Murielle
authors.initials: M
authors.lastname: Salomé
authors.affiliation: 5Central Facility for Electron Microscopy,University of Ulm,89069 Ulm,Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ziegler
authors.affiliation: 6Faculty of Veterinary and Animal Sciences,University of Chile,Santiago de Chile,Chile.
authors.forename: Maria S
authors.initials: MS
authors.lastname: Fernández
authors.affiliation: 6Faculty of Veterinary and Animal Sciences,University of Chile,Santiago de Chile,Chile.
authors.forename: José L
authors.initials: JL
authors.lastname: Arias
mesh_terms: D000818:Animals; D003400:Astacoidea / Q000737:chemistry*; D002119:Calcium Carbonate / Q000032:analysis*; D002130:Calcium Phosphates / Q000032:analysis*; D002686:Chitin / Q000032:analysis; D046911:Macromolecular Substances / Q000032:analysis; D018625:Microscopy, Atomic Force; D011506:Proteins / Q000032:analysis; D013057:Spectrum Analysis; D013270:Stomach / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: D002130:Calcium Phosphates; D046911:Macromolecular Substances; D011506:Proteins; C519480:amorphous calcium phosphate; D002686:Chitin; D002119:Calcium Carbonate
keywords: amorphous calcium carbonate; amorphous calcium phosphate; biomineralization; calcium storage; organic matrix