Ancient bristle worm jaws redefine metal in biology as a new class of bio-metals

Microscopic tests of Perinereis cultrifera jaws show ion‑coordinated proteins that harden toward the tips and display metal‑like, size‑dependent elasticity, supporting a new category called bio-metals that blend polymeric structure with metal‑like hardness; researchers used nanoindentation and manifold micromechanics to define bio-metals by hardness, strain behavior, and ion‑protein structure and plan to study more species and potential genetic links to material design.