Calcite fibre formation in modern brachiopod shells
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Show full item recordEditorial
Springer Nature
Date
2019-01-24Referencia bibliográfica
Roda, M. S., Griesshaber, E., Ziegler, A., Rupp, U., Yin, X., Henkel, D., ... & Checa, A. G. (2019). Calcite fibre formation in modern brachiopod shells. Scientific reports, 9(1), 1-15.
Sponsorship
This is a BASE-LINE Earth project supported by the European Union’s Horizon 2020 research and innovation program under grant agreement No. 643084. This is publication nr. 159 of Huinay Scientific Field Station.Abstract
The fibrous calcite layer of modern brachiopod shells is a hybrid composite material and forms a
substantial part of the hard tissue. We investigated how cells of the outer mantle epithelium (OME)
secrete calcite material and generate the characteristic fibre morphology and composite microstructure
of the shell. We employed AFM, FE-SEM, and TEM imaging of embedded/etched, chemically fixed/
decalcified and high-pressure frozen/freeze substituted samples. Calcite fibres are secreted by outer
mantle epithelium (OME) cells. Biometric analysis of TEM micrographs indicates that about 50% of
these cells are attached via hemidesmosomes to an extracellular organic membrane present at the
proximal, convex surface of the fibres. At these sites, mineral secretion is not active. Instead, ion
transport from OME cells to developing fibres occurs at regions of closest contact between cells and
fibres, however only at sites where the extracellular membrane at the proximal fibre surface is not
developed yet. Fibre formation requires the cooperation of several adjacent OME cells. It is a spatially
and temporally changing process comprising of detachment of OME cells from the extracellular organic
membrane, mineral secretion at detachment sites, termination of secretion with formation of the
extracellular organic membrane, and attachment of cells via hemidesmosomes to this membrane.