The unique fibrilar to platy nano- and microstructure of twinned rotaliid foraminiferal shell calcite
Metadatos
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Nature
Date
2023-02-07Referencia bibliográfica
Lastam, J... [et al.]. The unique fibrilar to platy nano- and microstructure of twinned rotaliid foraminiferal shell calcite. Sci Rep 13, 2189 (2023). [https://doi.org/10.1038/s41598-022-25082-9]
Patrocinador
GR9/1234 SCHM/930/11-2 German Research Council GR9/1234 SCHM/930/11-2 German Research CouncilRésumé
Diversification of biocrystal arrangements, incorporation of biopolymers at many scale levels and
hierarchical architectures are keys for biomaterial optimization. The planktonic rotaliid foraminifer
Pulleniatina obliquiloculata displays in its shell a new kind of mesocrystal architecture. Shell formation
starts with crystallization of a rhizopodial network, the primary organic sheet (POS). On one side
of the POS, crystals consist of blocky domains of 1 μm. On the other side of the POS crystals have
dendritic-fractal morphologies, interdigitate and reach sizes of tens of micrometers. The dendriticfractal
crystals are twinned. At the site of nucleation, twinned crystals consist of minute fibrils.
With distance away from the nucleation-site, fibrils evolve to bundles of crystallographically well
co-oriented nanofibrils and to, twinned, platy-blade-shaped crystals that seam outer shell surfaces.
The morphological nanofibril axis is the crystallographic c-axis, both are perpendicular to shell vault.
The nanofibrillar calcite is polysynthetically twinned according to the 60°/[100] (= m/{001}) twin
law. We demonstrate for the twinned, fractal-dendritic, crystals formation at high supersaturation
and growth through crystal competition. We show also that c-axis-alignment is already induced
by biopolymers of the POS and is not simply a consequence of growth competition. We discuss
determinants that lead to rotaliid calcite formation.