Biological strategy for the fabrication of highly ordered aragonite helices: The microstructure of the cavolinioidean gastropods
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Nature Publishing Group
BiomineralizationNanoscale biophysicsHelical fibrous microstructureCrystalline aragonite fibres
Checa González, A.; Macías-Sánchez, E.; Ramírez-Rico, J. Biological strategy for the fabrication of highly ordered aragonite helices: The microstructure of the cavolinioidean gastropods. Scientific Reports, 6: 25989 (2016). [http://hdl.handle.net/10481/44777]
SponsorshipFunding was provided by Research Projects CGL2013-48247-P of the Spanish Ministerio de Economía y Competitividad (MINECO) and Fondo Europeo de Desarrollo Regional (FEDER), and P10-RNM6433 of the Andalusian Consejería de Economía, Investigación, Ciencia y Empleo, of the Junta de Andalucía, and by the Research Group RNM363 (latter Institution).
The Cavolinioidea are planktonic gastropods which construct their shells with the so-called aragonitic helical fibrous microstructure, consisting of a highly ordered arrangement of helically coiled interlocking continuous crystalline aragonite fibres. Our study reveals that, despite the high and continuous degree of interlocking between fibres, every fibre has a differentiated organic-rich thin external band, which is never invaded by neighbouring fibres. In this way, fibres avoid extinction. These intra-fibre organic-rich bands appear on the growth surface of the shell as minuscule elevations, which have to be secreted differentially by the outer mantle cells. We propose that, as the shell thickens during mineralization, fibre secretion proceeds by a mechanism of contact recognition and displacement of the tips along circular trajectories by the cells of the outer mantle surface. Given the sizes of the tips, this mechanism has to operate at the subcellular level. Accordingly, the fabrication of the helical microstructure is under strict biological control. This mechanism of fibre-by-fibre fabrication by the mantle cells is unlike that any other shell microstructure.