title: The cuttlefish Sepia officinalis (Sepiidae, Cephalopoda) constructs cuttlebone from a liquid-crystal precursor.
abstract: 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.
authors.affiliation: 1] Departamento de Estratigrafía y Paleontología, Universidad de Granada, 18071 Granada, Spain [2] Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, 18071 Granada, Spain.
authors.forename: Antonio G
authors.initials: AG
authors.lastname: Checa
authors.affiliation: Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, 18071 Granada, Spain.
authors.forename: Julyan H E
authors.initials: JH
authors.lastname: Cartwright
authors.affiliation: Centro de Instrumentación Científica, Universidad de Granada, 18071 Granada, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Sánchez-Almazo
authors.affiliation: Centro de Ciências do Mar do Algarve, Universidade do Algarve, Faro, Portugal.
authors.forename: José P
authors.initials: JP
authors.lastname: Andrade
authors.affiliation: Departamento de Zoología, Universidad de Granada, 18071 Granada, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Ruiz-Raya
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000502:physiology* / Q000648:ultrastructure; D002113:Calcification, Physiologic; D049833:Sepia / Q000502:physiology*