Arthropods such as spiders and scorpions harden their fangs, claws, and stingers by incorporating small amounts of metals into their outer shells. Unlike bone, which incorporates metals as mineral crystals, in the shells, the metals are mixed in at the molecular level, hardening the structures and helping them stay sharp.
Now researchers have shown that scorpions show distinct patterns of metal enrichment across their weapons, a pattern the authors say likely reflects function (J. R. Soc. Interface 2026, DOI: 10.1098/rsif.2025.0523).
“Some [scorpions] rely almost entirely on their claws, while others on their stingers, which led me to suspect the enrichment is not by chance,” says Sam Campbell, a biologist at the University of Queensland who was involved in the work.
To map how metals are distributed, the researchers analyzed the claws and stingers of 18 scorpion species using X-ray-based techniques.
Across species, zinc clustered in either the claws or the stinger but rarely both, suggesting a trade-off in distribution. Scorpions with slender claws, which generate lower crushing forces, showed higher zinc levels, while others concentrated zinc in the stinger tip. Metals were also confined to high-stress regions such as the claw’s gripping teeth or the sharp end of the stinger.
But the most surprising pattern for Campbell involved iron. Stronger claws contained less of it, contrary to expectations that “higher crushing forces would require greater metal concentration,” he says. Instead, he suggests, iron may help the claws resist wear as they grip struggling prey.
Robert Schofield, a biophysicist and pioneer of arthropod biomineralization at the University of Oregon who was not involved in the study, says it is encouraging to see renewed attention to metal incorporation in arthropods.
He notes that enrichment patterns are usually consistent within scorpion families, making one result particularly striking. “In this case, a Hormuridae species shows a metal distribution more typical of another group.”
In the paper, the researchers also hint at a second trade-off within the stinger, where zinc and manganese concentrations vary inversely. Schofield says his own work has shown that zinc is concentrated at the tips of these structures, with manganese in underlying regions. Layering may help balance hardness with resistance to fracture, he says.
Kaushik Chatterjee, a bioengineer at the Indian Institute of Science who was not involved in the study, says these patterns could inform biomimetic design because “even small amounts of different ions can significantly change how a material behaves.” Chatterjee says that engineers often use trace elements to balance properties such as stability and wear. “Studies that explore how nature has tested materials over millennia directly enrich our field,” he says.
2026 American Chemical Society
