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Sep 14, 2013 09:43 AM EDT

Interlocking Gear Mechanism Discovered in Evolution of Juvenile Planthoppers

For the first time, scientists said they discovered evolutionary evidence of "gear mechanisms," as found in a clock, in a living being, according to a press release.

Previously believed to be a manmade invention, gear mechanisms were discovered in the hind legs of the juvenile Issus, a plant-hopping insect native to Europe. On its legs are opposing teeth that rotate and intermesh with each other like mechanical gears.

The scientists said this is the first evolutionary evidence of mechanical gears appearing in a living being. Their findings were published Friday in the journal Science.

Researchers at the University of Cambridge used high-speed video and anatomical analysis to study the planthopper's movements. Issus is the genus of the small planthoppers, which are native to Europe, North Africa, parts of the Middle East and the westernmost region of Asia.

"This precise synchronization would be impossible to achieve through a nervous system, as neural impulses would take far too long for the extraordinarily tight coordination required," said lead author Malcolm Burrows, a zoologist at Cambridge.

The gears lock the insect's leg movements together in near-perfect synchronization. The two hind legs will always move within 30 microseconds (one millionth of a second) of each other. If the planthopper did not have this ultra-precise timing with both hind legs, its high-powered jumps would result horribly for the insect.

"In Issus, the skeleton is used to solve a complex problem that the brain and nervous system can't," said Burrows. "This emphasizes the importance of considering the properties of the skeleton in how movement is produced."

The scientists said the mechanism cogs are only found in the Issus nymphs, their juvenile stage. When they shed key physical attributes in their transition to adulthood, the hind leg gears are left behind. The researchers theorized it is because the teeth of the cogs would not be reparable in adulthood.

If a gear's tooth were to break for a nymph, it could easily be repaired in the next "molt," or transformation stage. If that were to happen to an adult, the break would be permanent. Even one broken tooth would result in the entire system being thrown off.

Co-author Gregory Sutton, of the University of Bristol, said mechanisms and gears were only seen as manmade because insects like Issus went unnoticed.

"These gears are not designed," he said. "They are evolved - representing high speed and precision machinery evolved for synchronization in the animal world."

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