MODELING SPINES: Marine mollusks build their spiny shells with incremental secretions of material from the mantle, a cloak of soft tissue on the mollusk body. Researchers created a mathematical model for this process based on the mechanical deformation of the elastic mantle edge (yellow), which grows longer than the fixed shell edge (orange) and buckles when it temporarily attaches, before secreting new shell material into the deformed shape (1). Small variations in two parameters in the model—the growth rate and the heterogeneity of mantle bending stiffness at the mantle edge—accounted for a large diversity of spine structures
(2). IMAGES COURTESY OF DEREK MOULTON, REPRODUCED WITH PERMISSION FROM PNAS 110:6015-20, 2013
The paper
R. Chirat et al., “Mechanical basis of morphogenesis and convergent evolution of spiny seashells,” PNAS, 110:6015-20, 2013.
The spines adorning the shells of marine mollusks have evolved repeatedly across distantly related lineages, most likely because they help to fend off shell-crushing predators. But this functional explanation does not address the question of how spines form. In fact, the physical processes that shape spiny shell structures and that underlie their repeated emergence are not well understood.
To tackle that question, Derek Moulton of the Mathematical Institute at the University of Oxford and colleagues developed a mathematical model to predict how natural physical processes produce a diverse range of seashell spines.
Mollusks build their shells incrementally with secretions from an organ called the mantle, an ...
