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To cling to a deer, ticks must first pierce thick, hairy skin. Leaf cutter ants easily gnaw on tough tropical leaves. And scorpions use their tails to inject venom into prey several times the size of them.
Such wonders have long intrigued University of Oregon physicist Robert Schofield. How do these tiny creatures deliver such an outsized punch?
The answer, according to his new article published in Scientific reports, lies in the very atomic structure of their tools.
Scientists already knew that the mandibles, fangs and stingers of several species of invertebrates contain large amounts of heavy metals, such as zinc, copper and manganese, up to 20 percent by weight in some species. But they didn’t know how the metals bonded to the long-lasting proteins that are also found in the body parts of these invertebrates. (Watch the jaw-trap spiders snap their jaws at incredible speed.)
By analyzing proteins and heavy metals at the molecular level, Schofield and his colleagues learned that individual metal atoms are woven into proteins to create a strong and durable composite material, which they dubbed heavy element biomaterials.
“It’s really cool that adding these metals makes a tool more durable,” says Stephanie Crofts, a biologist at the College of the Holy Cross in Massachusetts who was not involved in the study. “This study is a good overview of how this occurs in a range of organisms, and it may be more common than we think.”
It’s also likely, Crofts adds, that such heavy-element biomaterials could inspire engineers creating new products, such as smaller cell phones and more rugged medical devices.
Better than biominerals
Of course, animals evolved in another way to form a sturdy natural material. Known as biomineralization, this widespread process occurs when proteins in an animal’s body wrap around large mineral crystals, such as bones or certain seashells. Bone is a potent mixture of minerals (mainly calcium carbonate) and proteins that provide the animal’s skeleton with the necessary flexibility, stretching and crushing far beyond what either or l other material could do on its own. (Learn more about bone science.)
But biomineralization has its limits: think of seashells, which can easily break. “Making something sharp with a biomineral would be like making a knife out of bricks,” says Schofield, who has been studying the jaws and claws of invertebrates since an ant crawled across the floor of his office in the late 1980s. 1980, the same office he now occupies.
Biominerals are not the answer for many invertebrates because they need sharp, sturdy body parts that can withstand continued use. A broken stinger, for example, would be a death sentence for a scorpion. So they found another way, says Schofield.
A powerful blend of metals and proteins
For his latest study, Schofield and his colleagues at the Pacific Northwest National Laboratory and the State of Oregon examined body parts of ants, spiders, scorpions, mollusks, and one type of sea worm. The team built miniature probes to test the mechanical properties of these parts and dissect them atom by atom.
They found that heavy metals, such as zinc and manganese, were distributed evenly throughout an invertebrate’s body part, unlike bone material and other biominerals. This atomic structure allows the body part to be sharper and to suffer more wear than if the proteins did not have the metals.
Another cost-saving benefit of heavy element biomaterials is that an ant uses 60% less energy to cut leaves than if it did not have this atomic structure, according to the team’s calculations. (Read about the Dracula ant, which can bite 5,000 times faster than the blink of an eye.)
Schofield still has many questions, such as whether these naturally resistant materials evolved one or more times in different groups of invertebrates, from crustaceans to centipedes.
Meanwhile, the discovery could create new potential for human tools, Crofts says.
For example, engineers are always looking for better strategies for making things that are small but don’t break easily, such as smartphones and portable medical devices like insulin pumps.
Making tools with that same atomic arrangement of proteins and heavy metals could lead to products that are light, strong, and resistant to daily handling, says Crofts, another example of how nature knows best.
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