Scorpions strengthen their deadly claws and stingers with heavy metals.

 

Armed with stingers and pincers, scorpions sport some of the most formidable weapons in the animal kingdom – weapons which, it turns out, are reinforced with heavy metals.

Now, scientists have found that different species incorporate those metals into their exoskeletons in different ways, depending on how they hunt and defend themselves.

The researchers examined the stingers and pincers of 18 scorpion species using X-rays and electron microscopes, and analyzed where metals such as zinc, iron, and manganese were being enriched.

They found that zinc is often concentrated right at the tip of the stinger, while manganese becomes the predominant metal further down the length.

However, in the pincers, zinc and iron appear primarily on the inner surface of the sharp tips, which helps withstand the impact generated when gripping and crushing prey.

However, this pattern does not always appear within the same species. If the pincers have a high zinc content, the stinger has a low zinc content, and conversely, if the stinger has a low zinc content, the pincers have a high zinc content.

"Through the microscopic analysis methods we used, we were able to identify individual transition metals with great precision, which allowed us to see how intricately nature has arranged these metals in the scorpion's weaponry," says Edward Vicenzi, a researcher at the Smithsonian Conservation Laboratory.

While scorpions generally share similar basic body structures, each species possesses specialized weapons.

For example, scorpions of the genus Opisthophthalmus have powerful pincers, but their tails are not particularly strong.

This is because Opisthophthalmus scorpions primarily use their forelegs. They use their forelegs to dig burrows, their tails mainly to crush prey with their pincers, and their stingers are utilized only as a secondary means.

However, scorpions of the genus Parabuthus are not called "thick-tailed scorpions" for nothing. Because their thick tails secrete fast-acting venom, catching prey is not a priority. This is evident simply by looking at their small pincers.

At first glance, one might expect that larger pincers would have higher metal content, and this study also established that hypothesis. However, the results were unexpected.

The analysis revealed that the pincers of species with long, weak crushing power had higher zinc content than those of species with strong crushing power.

While this may appear to be a result contrary to intuition, there is a logic to it.

"This points to a role for zinc beyond hardness, perhaps playing a bigger role in durability," says Sam Campbell, an evolutionary biologist at the University of Queensland in Australia.

"After all, long claws need to grasp prey and prevent it from escaping before being injected by venom.

"This is an interesting finding because it suggests an evolutionary relationship between how a weapon is used and the specific properties of the metal that reinforces it."

This is an interesting study with broad implications not only for scorpions but also for other arthropods that have reinforced their bodies with metal, such as spider fangs, ant jaws, and the stings of bees and wasps.

And let us take a moment to feel relieved by the fact that the prehistoric 'hell ants' and the giant metal spines growing on their heads have gone extinct.

This study was published in the Journal of the Royal Society Interface.