Igor Siwanowicz’s image of planthopper nymph gears won 9th place in the Olympus BioScapes International Digital Imaging Competition. Photo by Igor Siwanowicz, HHMI Janelia Research Campus, Ashburn, Virginia. Via Science Friday.
In September of 2013, Science published a paper by Malcolm Burrows and Gregory Sutton titled, “Interacting Gears Synchronize Propulsive Leg Movements in a Jumping Insect.” The two British biologists were discussing the fascinating structures they had found in the legs of small insects called planthoppers. At the top joints of each pair of legs, the tiny jumping insects had gears with interlocking teeth that synchronized the kicking motion between the two appendages, so that the planthoppers could jump straight rather than slightly to the left or right if one leg had acted even slightly before the other.
Covering the story back in September, Joseph Stromberg wrote for Smithsonian Magazine that:
To the best of our knowledge, the mechanical gear—evenly-sized teeth cut into two different rotating surfaces to lock them together as they turn—was invented sometime around 300 B.C.E. by Greek mechanics who lived in Alexandria. In the centuries since, the simple concept has become a keystone of modern technology, enabling all sorts of machinery and vehicles, including cars and bicycles.
On NPR’s Morning Edition, Adam Cole reported that Sutton, using a high-speed camera and lots of lights,
was able to observe a few kicks before switching out the insects. And he noticed something. They kicked with incredible, almost impossible synchrony — flexing within 0.05 milliseconds of each other.
That’s faster than neurons fire.
“So we were asking ourselves, ‘How in the world did they get such precise synchrony between the left and the right legs?’ ” Sutton says.
The answer lay in the gears, whose interlocking teeth force the legs to move at precisely the same time.
The small hopping insect Issus coleoptratus uses toothed gears (magnified above with an electron microscope) to precisely synchronize the kicks of its hind legs as it jumps forward. Photo by Malcom Burrows. Via Smithsonian Magazine.
Jane Lee, writing for National Geographic, spoke with Burrows, the paper’s other coauthor:
Adult planthoppers don’t have these structures, explained Burrows. When the nymphs molt into their adult bodies, they lose the gear wheels. Instead, the adults use a frictional strategy, where the parts of their hind legs closest to the body rub against each other to ensure synchronized movement.
Burrows isn’t sure why the adults don’t also use gear wheels when jumping. He speculates that it might be due to the fact that in nymphs, which molt about five to six times before becoming adults, lost gear teeth can be replaced with the next molt.
Since adult planthoppers don’t molt, they wouldn’t be able to replace damaged parts. “If you break your gear wheel a day after you molt, you’ll have to live with a broken gear wheel for the rest of your life,” Burrows explained.
And that life would probably be pretty short, he said, since the insect wouldn’t be able to effectively jump away from predators.
Why are we covering a story over a year old? Well, the photo at the top of this post came to our attention via Science Friday, where Rachel Nuwer covered the Picture of the Week by Igor Siwanowicz, a research specialist at Janelia Farm Research Campus in Virginia. Siwanowicz took several photos of planthopper gears by staining the exoskeleton with two fluorescent dyes and then using a laser to light up the different layers of dyed skeleton. You can read the SciFri article from last week here, and the following contain links to the original article from Science by Burrows and Sutton; Smithsonian Magazine‘s coverage; NPR’s Morning Edition on the entomo-gears; and NatGeo‘s piece.
Organikos 