Abstract

In every seashell there is a story. It is the story of the creature – a mollusc – that lived in and built the shell. Through an incremental growth process, the mollusc builds its own house, one layer at a time. It is a process that generates a shell surface with geometrical precision, regularity, and self-similarity, properties that have been observed and appreciated by palaeontologists and geometers alike for centuries, and formed a focus point in D'Arcy Thompson's famous book. In that process, there is a mechanical story as well: the form of the shell is driven by the mechanical interaction of a soft body and the rigid shell which it is itself secreting. We hypothesise that this interaction underlies a wide array of secondary patterns termed ornamentations, including ribs, needle sharp spines, travelling waves, and fractal-like structures. With such an abundance of shapes generated through a relatively simple growth process, the mollusc shell thus provides an excellent case study for morphomechanical pattern formation. And with a fossil record over 500 million years old and 100,000 extant species of shell building mollusc, mollusc shells all together tell a story of change and increasing complexity, making an excellent case study for evolution and the physical processes that govern it. In this talk I will present several chapters of the mollusc’s story and progress we have made in trying to understand the role of solid mechanics in their unique form.