Scorpions have been embedding metals into their weapons – their claws and stingers –for millions of years, and new University of Queensland research has placed a spotlight on this extraordinary evolutionary innovation.
PhD candidate Sam Campbell, from UQ’s School of the Environment, found that scorpions selectively draw zinc, iron and manganese into their weapons, making them sharper, harder and resistant to wear.
The study is the first to map this pattern across a snapshot of the scorpion family tree.
“Think of it like a suit of armour,” Mr Campbell said.
“The metals reinforce the scorpion’s exoskeleton making them tougher without adding bulk."
“Scorpions have been doing this for nearly 400 million years – long before humans ever figured out how to smelt metal.”
Working with colleagues Dr Hannah Wood, Dr Ed Vicenzi and Dr Thomas Lam at the Smithsonian, Mr Campbell examined the claws and stingers of 18 scorpion species from the museum's vast collection – specimens gathered by researchers from around the world over the past century.
“To find the metals, the team used a technique called micro X-ray fluorescence microscopy,” Mr Campbell said.
“Rather than using visible light, it fires a beam of X-rays at the sample and measures what bounces back – revealing a map of exactly which elements are present and where.
“A second technique, scanning electron microscopy, let us zoom in further and take precise measurements.
“It's the kind of technology you'd normally use to analyse rocks and minerals in a mine, but we were using it to look at scorpion claws.”
The results showed clear patterns – manganese was found only in the stinger, iron appeared only in the claws, zinc turned up in both – but in different amounts depending on the species.
“We found that zinc concentration flipped between weapons,” Mr Campbell said.
“This could suggest that scorpions that had more zinc in their stinger are likely to be using it more than the claws.
“The same could also be said for species with more zinc in the claws, with those potentially being the weapon of choice.
“It's essentially a cost-benefit analysis – the scorpion's body puts the reinforcement where it's needed most.”
One finding caught the team off guard, as they had expected the biggest, most powerful claws to contain the most iron.
Instead, it was the long, slender claws – the ones used to grip struggling prey before a sting – that were iron-rich.
“Those thin claws have to hold on while the prey is fighting to escape,” Mr Campbell said.
‘So it's not about crushing strength – it's about being tough enough not to wear down.”
Despite being one of Earth's oldest surviving creatures, scorpions are poorly understood and, of roughly 3,000 known species, only five have protected conservation status.
Mr Campbell hopes the findings will spark fresh interest, and open new doors for materials science.
“Scorpions have evolved a biological system that reinforces protein with metal, keeping weapons lightweight, thin and incredibly sharp,” he said.
“That's something engineers are still figuring out.
“We hope to now test whether different metal combinations actually change how hard or tough the weapons are, and whether the metals in scorpion venom connect to those found in the stinger itself.”
The research is published in Royal Society Interface.
