Crystallographic control on the substructure of nacre tablets

Checa, António; Mutvei, Harry; Osuna‐Mascaró, Antonio J.; Bonarski, J.; Faryna, M.; Berent, Katarzyna; Pina, Carlos M.; Rousseau, Marthe; Macías‐Sánchez, Elena

doi:10.1016/j.jsb.2013.07.014

Cited by 34 publications

(50 citation statements)

References 52 publications

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“…3C–E). These lineations have also been revealed in the nacre of bivalves and gastropods [55], [56], in the foliated aragonite of monoplacophorans [57] and in the prismatic aragonitic spikes of anomalodesmatan bivalves [34] and have been recently demonstrated by TEM [58] and EBSD [59] to be parallel to the a -axis of aragonite. This therefore suggests that the bosses in Neotrigonia are short prismatic units of aragonite consisting of several crystals (sectors) which are polycyclically twinned on {110}.…”

Section: Resultsmentioning

confidence: 68%

Early Stage Biomineralization in the Periostracum of the ‘Living Fossil’ Bivalve Neotrigonia

et al. 2014

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A detailed investigation of the shell formation of the palaeoheterodont ‘living fossil’ Neotrigonia concentrated on the timing and manufacture of the calcified ‘bosses’ which stud the outside of all trigonioid bivalves (extant and fossil) has been conducted. Electron microscopy and optical microscopy revealed that Neotrigonia spp. have a spiral-shaped periostracal groove. The periostracum itself is secreted by the basal cell, as a thin dark pellicle, becoming progressively transformed into a thin dark layer by additions of secretions from the internal outer mantle fold. Later, intense secretion of the internal surface of the outer mantle fold forms a translucent layer, which becomes transformed by tanning into a dark layer. The initiation of calcified bosses occurred at a very early stage of periostracum formation, deep within the periostracal groove immediately below the initialmost dark layer. At this stage, they consist of a series of polycyclically twinned crystals. The bosses grow as the periostracum traverse through the periostracal groove, in coordination with the thickening of the dark periostracal layer and until, upon reaching the mantle edge, they impinge upon each other and become transformed into large prisms separated by dark periostracal walls. In conclusion, the initial bosses and the external part of the prismatic layer are fully intraperiostracal. With later growth, the prisms transform into fibrous aggregates, although the details of the process are unknown. This reinforces the relationships with other groups that have the ability to form intraperiostracal calcifications, for example the unionoids with which the trigonioids form the clade Paleoheterodonta. The presence of similar structures in anomalodesmatans and other euheterodonts raises the question of whether this indicates a relationship or represents a convergence. The identification of very early calcification within an organic sheet has interesting implications for our understanding of how shells may have evolved.

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Section: Resultsmentioning

confidence: 68%

Early Stage Biomineralization in the Periostracum of the ‘Living Fossil’ Bivalve Neotrigonia

et al. 2014

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“…We performed both AFM and S/TEM on single tablets (Fig. 4 ), with both revealing the globular texture typical of nacre 17 , 22 , 23 and other biominerals 10 , 24 . AFM phase contrast images (which enable the detection of variations in adhesion, friction and viscoelasticity 25 ; see explanation in Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

Transformation of ACC into aragonite and the origin of the nanogranular structure of nacre

Macías‐Sánchez

Willinger

Pina

et al. 2017

Sci Rep

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Currently a basic tenet in biomineralization is that biominerals grow by accretion of amorphous particles, which are later transformed into the corresponding mineral phase. The globular nanostructure of most biominerals is taken as evidence of this. Nevertheless, little is known as to how the amorphous-to-crystalline transformation takes place. To gain insight into this process, we have made a high-resolution study (by means of transmission electron microscopy and other associated techniques) of immature tablets of nacre of the gastropod Phorcus turbinatus, where the proportion of amorphous calcium carbonate is high. Tablets displayed a characteristic nanoglobular structure, with the nanoglobules consisting of an aragonite core surrounded by amorphous calcium carbonate together with organic macromolecules. The changes in composition from the amorphous to the crystalline phase indicate that there was a higher content of organic molecules within the former phase. Within single tablets, the crystalline cores were largely co-oriented. According to their outlines, the internal transformation front of the tablets took on a complex digitiform shape, with the individual fingers constituting the crystalline cores of nanogranules. We propose that the final nanogranular structure observed is produced during the transformation of ACC into aragonite.

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“…While modern cephalopods have only the shell of Nautilus as a true shell, our understanding of cephalopod biomineralization has been advanced by studies of nacre in Nautilus shells (Checa et al . ) as well as other cephalopod biomineral structures such as the paper nautilus, Argonauta nodosa , shell (Wolfe et al . ) and the cuttlebone (Cusack and Chung ).…”

Section: Molluscs – Where Two Polymorphs Meetmentioning

confidence: 99%

Biomineral electron backscatter diffraction for palaeontology

Cusack

2015

Palaeontology

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Electron backscatter diffraction (EBSD) originated in materials science and has transferred to biomineral research providing insight into fossil and modern biominerals. An electron microscopy technique, EBSD requires a fine polished sample surface where the electron beam diffracts in the first few lattice layers, identifying mineral, polymorph and crystallographic orientation. The technique is particularly well suited for the analysis of modern and fossil calcium carbonate biominerals, where it provides key insight into biological control of mineral formation such as in molluscs and brachiopods. EBSD readily identifies original and secondary mineralogy, which helps to inform our understanding of biomineral evolution such as the identification of original aragonite in Silurian trimerellid brachiopods. As a technique to identify and thus avoid the inclusion of secondary minerals in proxy organisms such as corals, EBSD can be used to ensure accuracy of palaeoproxy data. Even when fossil systems have no modern equivalents, EBSD can provide key data to determine functional mechanisms such as in the lenses of schizochroal eyes of phacopine trilobites. These few examples illustrate that EBSD is proving to be a valuable component of the palaeontology toolkit.

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Crystallographic control on the substructure of nacre tablets

Cited by 34 publications

References 52 publications

Early Stage Biomineralization in the Periostracum of the ‘Living Fossil’ Bivalve Neotrigonia

Early Stage Biomineralization in the Periostracum of the ‘Living Fossil’ Bivalve Neotrigonia

Transformation of ACC into aragonite and the origin of the nanogranular structure of nacre

Biomineral electron backscatter diffraction for palaeontology

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