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GEOREF RECORD

Amorphous calcium carbonate in the shell material of the brachiopod Megerlia truncata

Erika Griesshaber, Klemens Kelm, Angelika Sehrbrock, Werner Mader, Joerg Mutterlose, Uwe Brand and Wolfgang W. Schmahl
Amorphous calcium carbonate in the shell material of the brachiopod Megerlia truncata
European Journal of Mineralogy (August 2009) 21 (4): 715-723

Abstract

Terebratulide brachiopod shells have a thin, hard outer nanocrystalline calcite layer and a hybrid fibre composite inner layer with CaCO (sub 3) fibres embedded in an organic matrix. Here we report our observation by transmission electron microscopy (TEM) of a large compartment filled with amorphous calcium carbonate (ACC) in the shell of the modern brachiopod Megerlia truncata. The compartment has the typical shape and size of fibrous calcite crystals composing the inorganic component of the hybrid fibre composite secondary shell layer. The ACC compartment is adjacent to an inclusion of foreign material that is entirely incorporated into the shell. It has most probably been produced in the course of shell reparation. Under TEM imaging conditions the amorphous carbonate crystallized in situ to vaterite and calcite. The distribution pattern of the organic component of the shell material is spatially differentiated. While in the outer, nanocrystalline primary shell layer we do not observe any organic material between the crystallites by TEM, the CaCO (sub 3) fibres of the secondary layer are surrounded by an organic sheath. In the innermost segment of the secondary layer, in addition to the organic sheaths, thick organic membranes are present. The compartment containing ACC is located between two, 1-2 mu m thick, organic membranes. Our observations indicate that brachiopod shell formation may occur via an ACC precursor that is produced in an initial stage prior to the crystallization of calcite.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 21
Serial Issue: 4
Title: Amorphous calcium carbonate in the shell material of the brachiopod Megerlia truncata
Affiliation: Ludwig-Maximilians Universitaet Muenchen, Department fuer Geo- und Umweltwissenschaften, Munich, Federal Republic of Germany
Pages: 715-723
Published: 200908
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 54
Accession Number: 2009-085441
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Secondary Affiliation: Forschungszentrum Caesar, DEU, Federal Republic of GermanyUniversitaet Bonn, DEU, Federal Republic of GermanyRuhr-Universitaet Bochum, DEU, Federal Republic of GermanyBrock University, CAN, Canada
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200946
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