abstract
We confirm with high-resolution techniques the existence of mineral bridges between superposed nacre tablets. In the towered nacre of both gastropods and the cephalopod Nautilus there are large bridges aligned along the tower axes, corresponding to gaps (150-200 nm) in the interlamellar membranes. Gaps are produced by the interaction of the nascent tablets with a surface membrane that covers the nacre compartment. In the terraced nacre of bivalves bridges associated with elongated gaps in the interlamellar membrane (>100 nm) have mainly been found at or close to the edges of superposed parental tablets. To explain this placement, we hypothesize that the interlamellar membrane breaks due to differences in osmotic pressure across it when the interlamellar space below becomes reduced at an advanced stage of calcification. In no cases are the minor connections between superimposed tablets (<60 nm), earlier reported to be mineral bridges, found to be such. (C) 2011 Elsevier Inc. All rights reserved.
keywords
ORGANIC MATRIX LAYERS; ABALONE NACRE; SHELL; DIFFRACTION; GROWTH; STRENGTH; MOLLUSCA; BIVALVIA; CRYSTAL
subject category
Biochemistry & Molecular Biology; Biophysics; Cell Biology
authors
Checa, AG; Cartwright, JHE; Willinger, MG
Groups
Projects
RMNE-UA-National Network of Electron Microscopy (REDE/1509/RME/2005 )
Structural and chemical characterization at the nanometer scale (PTDC/CTM/100468/2008)
acknowledgements
We thank Achim Klein (Fritz-Haber Institut, Berlin) and Fabian Perez-Willard (Zeiss Optronics GmbH, Oberkochen, Germany) for sample preparation and analysis. Funding was provided by Projects CGL2007-60549, CGL2010-20748-CO2-01 and FIS2010-22322-CO2-02 of the Spanish Ministerio de Ciencia e Innovacion, Projects REDE/1509/RME/2005 and PTDC/CTM/100468/2008 of the Portuguese Foundation for Science and Technology (FCT), the Research Group RNM190 (Junta de Andalucia), and the European COST Action TD0903.