This was all over Reddit and ScienceDaily today, because it’s cool. Biologists have found the first example of machine-like gears in a living organism, a critter called an adolescent Issus:
Through a combination of anatomical analysis and high-speed video capture of normal Issus movements, scientists from the University of Cambridge have been able to reveal these functioning natural gears for the first time. The findings are reported in the latest issue of the journal Science.
The gears in the Issus hind-leg bear remarkable engineering resemblance to those found on every bicycle and inside every car gear-box. Each gear tooth has a rounded corner at the point it connects to the gear strip; a feature identical to human-made gears such as bike gears — essentially a shock-absorbing mechanism to stop teeth from shearing off.
The gear teeth on the opposing hind-legs lock together like those in a car gear-box, ensuring almost complete synchronicity in leg movement — the legs always move within 30 ‘microseconds’ of each other, with one microsecond equal to a millionth of a second.
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“This precise synchronisation 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 Professor Malcolm Burrows, from Cambridge’s Department of Zoology.
“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.
“In Issus, the skeleton is used to solve a complex problem that the brain and nervous system can’t.”
Once the insects grow up, the gears are replaced by friction pads – to avoid problems when teeth are bent or broken in their tiny transmissions. There are photos of the gears at the link.