Thermodynamic Aspects of Molluscan Shell Ultrastructural Morphogenesis

Abstract

Over the years, molluscan shells have become an exemplar model system to study the process of mineral formation by living organisms, the process of biomineralization. Typically, the shells consist of a number of mineralized ultrastructural motifs, each exhibiting a specific mineral‐organic composite architecture. These are made of calcium carbonate building blocks having a well‐defined three‐dimensional morphology that is significantly different from the shape of inorganically formed counterparts. Shell ultrastructures are known to form via a biologically controlled extracellular mineralization pathway in which the organism has no direct control over mineral formation. The cellular tissue, responsible for shell biomineralization, forms an organic framework and sets‐up the physical conditions necessary for the deposition of a specific morphology, whereas the growth of the mineral part of the shell proceeds spontaneously via the process of self‐assembly. In this feature article, the ability to employ thermodynamic models from classical materials science to describe the process of self‐assembly and structural evolution of a variety of shell architectures is reviewed. Having the potential to offer an analytical framework to express ultrastructure formation in time and in space, these models not only provide a deeper insight into shell biomineralization, but also suggest tools for novel composite materials design.