abstract
The nacre of gastropod molluscs is intriguingly stacked in towers. It is covered by a surface membrane, which protects the growing nacre surface from damage when the animal withdraws into its shell. The surface membrane is supplied by vesicles that adhere to it on its mantle side and secretes interlamellar membranes from the nacre side. Nacre tablets rapidly grow in height and later expand sideways; the part of the tablet formed during this initial growth phase is here called the core. During initial growth, the tips of the cores remain permanently submerged within the surface membrane. The interlamellar membranes, which otherwise separate the nacre tablet lamellae, do not extend across cores, which are aligned in stacked tablets forming the tower axis, and thus towers of nacre tablets are continuous along the central axis. We hypothesize that in gastropod nacre growth core formation precedes that of the interlamellar membrane. Once the core is complete, a new interlamellar membrane, which covers the area of the tablet outside the core, detaches from the surface membrane. In this way, the tower-like growth of gastropod nacre becomes comprehensible.
keywords
ORGANIC MATRIX; ABALONE SHELL; LAYER; DIFFRACTION; NUCLEATION
subject category
Science & Technology - Other Topics
authors
Chec, AG; Cartwright, JHE; Willinger, MG
Groups
acknowledgements
Wewish to express our profoundest appreciation to H. Nakahara (1928-2001). In noticing the existence of the surface membrane and of an organic core along the axes of the nacre towers, he largely inspired our work, which also benefitted from the study of his unique material. We thank M. Kakei (Meikai University) for providing TEM material of H. Nakahara, A . Hernandez-Hernandez (Consejo Superior de Investigaciones Cientficas Universidad de Granada) for sampling preparation with her own fixative and decalcification technique, M. Rousseau (Museum Natural d'Histoire Naturelle, Paris) for Fig. 1B, and E. M. Harper (Cambridge University) for critical revision. This work was supported by Research Project CGL2007- 60549 ( Ministerio de Ciencia e Innovacion) and the Research Group RNM190 ( Junta de Andaluc a).