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For Power And Precision, Leaping Insect Gets Into Gear

posted 13 Sept 2013, 06:23 by Mpelembe   [ updated 13 Sept 2013, 06:24 ]

Video showing the first known example of a gear mechanism in nature has been released by British scientists. Their research shows that the common garden insect, Issus, has hind-leg joints containing cog-like strips that intermesh when moving, allowing it to leap with power and precision.

CAMBRIDGE, ENGLAND, UK (BURROWS/SUTTON) - Scientists have discovered that a common plant-hopping inset has legs with a natural gear mechanism. The discovery, by British academics Professor Malcolm Burrows and Gregory Sutton, proves that gear mechanisms previously thought to be solely man-made have an evolutionary precedent.

The juvenile Issus insect, found in gardens across Europe, has hind-leg joints with curved cog-like strips of opposing 'teeth' that intermesh, rotating like mechanical gears to synchronise the animal's legs when it launches into a jump. Seen in high-speed video capture video, the Issus's hind-leg gears resemble those found in bicycles and car gear-boxes.

Each 'gear tooth' has a rounded corner where it connects to the gear strip, essentially a shock-absorbing mechanism to stop teeth from shearing off. It's a feature identical to man-made gear mechanisms. The legs always move within 30 'microseconds' of each other. One microsecond is equal to a millionth of a second. This is critical for the powerful jumps that are this insect's primary mode of transport. Burrows and Sutton say that even miniscule discrepancies in synchronisation between the velocities of its legs at the point of propulsion would result in 'yaw rotation' - causing the Issus to spin out of control.

"By developing mechanical gears, the Issus can just send nerve signals to its muscles to produce roughly the same amount of force - then if one leg starts to propel the jump the gears will interlock, creating absolute synchronicity," said Burrows, from Cambridge University's Department of Zoology.

"We usually think of gears as something that we see in human designed machinery, but we've found that that is only because we didn't look hard enough," added co-author Gregory Sutton, now at the University of Bristol.

The mechanistic gears are only found in the insect's juvenile stages and lost in the final transition to adulthood.

Unlike man-made gears, each gear tooth is asymmetrical and curved towards the point where the cogs interlock. Man-made gears need a symmetric shape to work in both rotational directions, whereas the Issus gears are only powering one way to launch the animal forward.

The Issus is the first example of a natural cog mechanism with an observable function, say the scientists. Their findings are reported in the latest issue of the journal Science.