How It Works

Vegetarian ants have steak-knife teeth

- WORDS JOANNA THOMPSON

Tiny arthropods such as ants, spiders and scorpions routinely bite, sting or otherwise pierce tough material like wood and skin. Recent research has shed light on what gives one group of leafcutter ants (Atta cephalotes) their biting edge. Using powerful microscope­s, scientists have discovered a web of zinc atoms woven into the biological structure of the ants’ jaws, lending them the durability of stainless-steel knives. This smooth distributi­on of zinc allows the edge of the ants’ teeth to form a fine point, and keeps them sharp for a long time.

“The tiny animals who had this material, their muscles are microscopi­c compared to ours,” said Robert Schofield, a biophysici­st at the University of Oregon. The trick is that ants and other metal-mouthed arthropods leverage their sharp chompers to apply precisely the right amount of cutting force to slice through leaves or hide. Ant teeth contain a lot of zinc, but it remained unclear how those metal atoms were arranged, and how that helped the ants’ bite. By examining the material make-up of leafcutter ant teeth under an ion-beam microscope before and after biting, the researcher­s were able to calculate the hardness, sharpness and durability of the teeth.

The tiny, serrated ‘teeth’ lining the inside edge of an ant’s mandible are coated in a smooth blend of proteins crisscross­ed with zinc. This material, known as a ‘heavy element biomateria­l’, easily matches human tooth enamel for strength. It also makes an ant’s tooth much better for slicing and dicing, since the blocky calcium phosphate crystals found in enamel can’t form extremely sharp edges. That would be like trying to fashion a knife “out of chunks of gravel”, Schofield said. Zinc, however, does not form blocky crystals; instead it stays evenly distribute­d throughout the protein mixture. That fine consistenc­y allows for the sharp edges of the teeth.

Metallic reinforcem­ents don’t stop with ant teeth. Other invertebra­tes also weave zinc or a similar metal, manganese, into their tiny toolkits. Schofield and his team found that giant clam worms pack jaws infused with up to 18 per cent zinc. Similarly, scorpion stings and spider fangs employ a mix of zinc and manganese atoms to ensure that these slender, needle-like structures can puncture tough flesh without breaking.

 ?? ?? A leafcutter ant (Atta cephalotes) using its metal-laced mandibles to cut through a leaf
A leafcutter ant (Atta cephalotes) using its metal-laced mandibles to cut through a leaf

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