Overview
- The Nature Communications paper published Tuesday used advanced 3D X-ray tensor tomography at MAX IV, the Swiss Light Source and the ESRF to map tusk structure at atomic-to-millimetre scales.
- Scans showed an inner right-handed dentin helix and an outer left-handed cementum helix that meet at a complex transition zone inside the tusk.
- Mechanical analysis indicates the two counter-rotating helices increase resistance to bending and torsion, which helps explain why the narwhal’s single tusk grows straight rather than curved.
- The team also identified preserved annual growth layers similar to tree rings that can record age to about 80 years and may let scientists reconstruct individual life histories and environmental conditions.
- Authors say the result has material-design implications and will guide follow-up studies of growth-layer chemistry and tusk formation while the tusk’s primary biological role remains debated between sexual-signaling and sensory hypotheses.