Growth of a Tesselation
Team Led by MoA Researchers Mason Dean and Peter Fratzl Present New Findings
Hyomandibula - Tesserae shapes and their growth. Image: Mason Dean
The skeletons of sharks and rays, which consist of cartilage and are armored with a covering of mineralized tiles (tesserae), pose a mathematical challenge: How can continuous coverage be maintained as the skeleton grows? For a study published in last December's issue of Advanced Science, microCT and custom visual data analyses of growing skate skeletons were used to systematically examine the tessellation patterns and morphology of the many thousands of interacting tesserae that cover the hyomandibula, a skeletal element critical for feeding.
The contributing researchers, including MoA members Peter Fratzl, Mason Dean, Binru Yang, and Jana Cicierska-Holmes, were able to show that stingray cartilage solves the problem of growing a mineralized surface that cannot be inherently remodeled by dividing the crust into tiles connected by collagenous fibers. The experimentally observed self-similar growth may be based on a simple growth rule in which the elongation of these fibers controls the rate of attachment to the polygonal tesserae by mechanosensitive cells that sit between these fibers. In this way, the integrity of the mosaic can be maintained at all times during growth without the need for overall control of mineral deposition rates, provided that the cells in the interstices are mechanosensitive and deposit mineral in response to strain.
Congratulations to the scientists involved for unraveling the mystery of this exciting and highly complex growth process!
The article is available open access in the Wiley Open Library: https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202407641