High-resolution structural and elemental analyses of calcium storage structures synthesized by the noble crayfish Astacus astacus.
During premolt, crayfish develop deposits of calcium ions, called gastroliths, in their stomach wall. The stored calcium is used for the calcification of parts of the skeleton regularly renewed for allowing growth. Structural and molecular analyses of gastroliths have been primarily performed on three crayfish species, Orconectes virilis, Procambarus clarkii, and more recently, Cherax quadricarinatus. We have performed high-resolution analyses of gastroliths from the native noble crayfish, Astacus astacus, focusing on the microstructure, the mineralogical and elemental composition and distribution in a comparative perspective. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) observations showed a classical layered microstructure composed of 200-nm diameter granules aligned along fibers. These granules are themselves composed of agglomerated nanogranules of 50nm-mean diameters. Denser regions of bigger fused granules are also present. Micro-Raman spectroscopy show that if A. astacus gastroliths, similarly to the other analyzed gastroliths, are mainly composed of amorphous calcium carbonate (ACC), they are also rich in amorphous calcium phosphate (ACP). The presence of a carotenoid pigment is also observed in A. astacus gastrolith contrary to C. quadricarinatus. Energy-dispersive X-ray spectroscopy (EDX) analyses demonstrate the presence of minor elements such as Mg, Sr, Si and P. The distribution of this last element is particularly heterogeneous. X-ray absorption near edge structure spectroscopy (XANES) reveals an alternation of layers more or less rich in phosphorus evidenced in the mineral phase as well as in the organic matrix in different molecular forms. Putative functions of the different P-comprising molecules are discussed.
Sorbonne Universités, Paris, France; UMR BOREA, Biologie des Organismes et des Ecosystèmes Aquatiques, UMR MNHN/CNRS 7208/UPMC/UCN/UA/IRD 207, Muséum National d'Histoire Naturelle, 75005 Paris, France. Electronic address: gluquet@mnhn.fr.
Gilles
G
Luquet
ID21, European Synchrotron Radiation Facility, 38000 Grenoble, France.
Murielle
M
Salomé
Central Facility for Electron Microscopy, University of Ulm, 89069 Ulm, Germany.
Andreas
A
Ziegler
Sorbonne Universités, Paris, France; UMR MONARIS, De la Molécule aux Nano-Objets: Réactivité, Interactions et Spectroscopies, UMR 8233 CNRS-Université Pierre et Marie Curie, 75005 Paris, France.
Céline
C
Paris
Sorbonne Universités, Paris, France; UMR MONARIS, De la Molécule aux Nano-Objets: Réactivité, Interactions et Spectroscopies, UMR 8233 CNRS-Université Pierre et Marie Curie, 75005 Paris, France.
Aline
A
Percot
Sorbonne Universités, Paris, France; Institut de Systématique, Evolution, Biodiversité, Muséum National d'Histoire Naturelle, 75005 Paris, France.
Yannicke
Y
Dauphin
D000818:Animals; D003400:Astacoidea / Q000033:anatomy & histology* / Q000737:chemistry; D002113:Calcification, Physiologic; D002118:Calcium / Q000378:metabolism*; D002119:Calcium Carbonate / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis
D002130:Calcium Phosphates; C020243:calcium phosphate; D002119:Calcium Carbonate; D002118:Calcium
Amorphous calcium carbonate; Amorphous calcium phosphate; Biomineralization; Calcium storage; Crustacea; Phosphorus