The cuttlefish Sepia officinalis (Sepiidae, Cephalopoda) constructs cuttlebone from a liquid-crystal precursor
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AutorCheca González, Antonio; Cartwright, Julyan H. E.; Sánchez-Almazo, Isabel; Andrade, José P.; Ruiz-Raya, Francisco
Checa González, A.; et al. The cuttlefish Sepia officinalis (Sepiidae, Cephalopoda) constructs cuttlebone from a liquid-crystal precursor. Scientific Reports, 5: 11513 (2015). [http://hdl.handle.net/10481/37170]
PatrocinadorThis research was funded by projects CGL2010-20748-CO2-01 (to A.G.C. and F.R.R.), CGL2013-48247-P (to A.G.C. and I.S.A.) and FIS2013-48444-C2-2-P (to J.H.E.C.) of the Spanish Ministerio de Ciencia e Innovación, and RNM6433 (to A.G.C., J.H.E.C. and I.S.A.), of the Andalusian Consejería de Innovación Ciencia y Tecnología, and 31.03.05.FEP.002 (Sepiatech, PROMAR program) of the Portuguese Ministério da Agricultura e do Mar, Portugal (to J.P.A.). A.G.C. and J.H.E.C. also acknowledge the Research Group RNM363 (Junta de Andalucía) and the FP7 COST Action TD0903 of the European Community.
Cuttlebone, the sophisticated buoyancy device of cuttlefish, is made of extensive superposed chambers that have a complex internal arrangement of calcified pillars and organic membranes. It has not been clear how this structure is assembled. We find that the membranes result from a myriad of minor membranes initially filling the whole chamber, made of nanofibres evenly oriented within each membrane and slightly rotated with respect to those of adjacent membranes, producing a helical arrangement. We propose that the organism secretes a chitin–protein complex, which self-organizes layer-by-layer as a cholesteric liquid crystal, whereas the pillars are made by viscous fingering. The liquid crystallization mechanism permits us to homologize the elements of the cuttlebone with those of other coleoids and with the nacreous septa and the shells of nautiloids. These results challenge our view of this ultra-light natural material possessing desirable mechanical, structural and biological properties, suggesting that two self-organizing physical principles suffice to understand its formation.