Image: Flea anatomy
Gregory Sutton and Malcolm Burrows via JEB
This photomicrograph shows the anatomical features of the hedgehog flea, including its trochanter (the flea's "knee") and its tarsus (the "toes"). The scale bar indicates 500 microns, which is roughly five times the width of a human hair.
By Senior writer
updated 2/10/2011 2:49:37 PM ET 2011-02-10T19:49:37

Fleas perform an amazing feat when they jump, and the mechanics behind the tiny, bloodsucking pests' acrobatics have been studied — and debated — for a long time. But new research may have settled one major question: How do fleas lift themselves off the ground?

It turns out the tiny insects push off the ground using their shins and feet.

"It's been known fleas are incredible jumpers for 1,000 years," said Gregory Sutton, a research fellow at the University of Cambridge in England. "If you see fleas in your hand and you see them jump and you realize how small they are, it doesn't take much to realize these guys are catapulting themselves huge numbers of body lengths," said Sutton, who along with a colleague completed this most recent study of the mechanics of a flea's jump, an athletic effort that catapults the fleas 50 to 100 times their body length.

One mystery solved, another remains
Fleas jump more quickly and with more force, than would be possible using muscle. This mystery was solved in 1967, when researcher Henry Bennet-Clark discovered that the fleas, using an elastic pad made of a protein called resilin and, like a tensed spring, release the pad to catapult themselves into the air.

  1. Science news from NBCNews.com
    1. NOAA
      Cosmic rays may spark Earth's lightning

      All lightning on Earth may have its roots in space, new research suggests.

    2. How our brains can track a 100 mph pitch
    3. Moth found to have ultrasonic hearing
    4. Quantum network could secure Internet

But this discovery gave rise to another debate that remained unresolved: How did the fleas transfer the force from the spring mechanism to the ground to lift off? Bennet-Clark believed a flea pushed down through its tibia and tarsus (equivalent to a human shin and foot or toe, respectively). Meanwhile, fellow flea researcher Miriam Rothschild believed that fleas pushed off using their trochantera (equivalent to human knees).

Sutton and study collaborator Malcolm Burrows, also of the University of Cambridge, resolved the debate using high-speed cameras, an electron microscope and computer modeling, plus 10 hedgehog fleas (donated by the Tiggywinkles Wildlife Hospital Trust).

The evidence
Before fleas take off on a jump, their knees appear to rest on the ground, creating an important sticking point in the debate.

With the aid of the cameras, the researchers filmed the fleas jumping 51 times. In 45 of those jumps, the fleas' feet and knees were on the ground when the flea pushed off. However, in the remaining six, the knees were both clear of the ground at that time, indicating they did not transfer the force of the jump to the ground. In all of the jumps, the feet touched the ground.

Pictures taken through the microscope revealed that spiny gripping structures — which come in handy while bracing during lift off — covered the fleas' feet and shins. The knees, meanwhile, were smooth. And finally, the researchers used computer models to run simulations of both jumping theories. Here, too, evidence supported the lower-leg push-off theory. 

"We pretty much discounted the hypothesis that force is going through the knee," Sutton said. Their work appears in Thursday's issue of the Journal of Experimental Biology.

This doesn't mean there aren't more mysterious aspects to flea jumping ripe for exploration. The team plans to look at how the fleas control their jumps.

"We never observed any time when one leg would extend without the other one, so we want to figure how the fleas do that," Sutton said, explaining, "there doesn't appear to be any mechanical connection between them, but they fire off at exactly the same time."

You can follow LiveScience writer Wynne Parry on Twitter @Wynne_Parry.

© 2012 LiveScience.com. All rights reserved.

Video: See how a flea jumps

Explainer: Top 10 oddballs of the animal world

  • Image: Platypus
    Healesville Sanctuary

    From the outside, the platypus looks like a grade-school art project assembled by a kid too busy making spitballs to pay attention in class. The creature, which is classified as a mammal, has a duck's bill and webbed feet, lays eggs like a reptile, but has fur and rears its young on milk.

    Researchers say the platypus genome is equally cobbled together from bird, reptile and mammalian lineages. One more oddity: Males can deliver venom from tiny spurs on each hind limb. Click on the "Next" arrow above to learn about nine more oddballs in the animal world.

    More info: Mixed-up platypus genome unscrambled

    — By John Roach, msnbc.com contributor

  • Colossal squid has plate-sized eye

    AP

    In April 2008, scientists in New Zealand looked a thawing colossal squid in the eye and discovered that the eye is, well, colossal — about the size of a dinner plate. That makes it the largest animal eye on Earth. Fishermen caught the 1,000-pound creature last year in Antarctic waters and froze it intact for scientific study. Colossal squids can reach 46 feet in length and have tentacles equipped with suckers and hooks. Scientists believe the creatures can descend to 6,500 feet and are active, aggressive hunters.

    More info: Huge squid caught, could be biggest ever

  • Aye-aye gives grubs the finger

    Duke University Lemur Center

    The aye-aye is a bushy-tailed primate from Madagascar with big eyes and bat ears. But call it funny-looking and it just might extend its extra-long middle finger in your general direction. The member of the lemur family otherwise uses the extended digit to fish out grubs from the crevices of trees. Captive aye-ayes such as the one shown here from Duke University are teaching scientists about the evolution of color vision.

    Learn more about the brainiac of all lemurs

  • Star-nosed mole sniffs out food, fast

    Image: Star-nosed mole
    Kenneth C. Catania / Vanderbilt

    The fleshy appendages that ring the snout of the star-nosed mole, shown here, make it one strange-looking creature. But when it comes to eating, those 22 tentacles help the mole detect and devour food faster than the human eye can follow — in a fraction of a second. Researchers say the speedy feeding allows the mole to prey on small insect larvae that would otherwise be too energetically costly to eat. The creature lives and forages under the cover of marshes and wetlands along the east coast of North America.

  • Burrowing toad is genetically different

    Robert Puschendorf

    For an amphibian, the stocky and squat Mexican burrowing toad doesn't look all that strange, but it's actually unique. A global conservation program called EDGE of Existence ranks the toad as the most "evolutionarily distinct" amphibian in the world. A fruit bat, polar bear, killer whale, kangaroo and human are all more closely related to one another than the toad is to any other species, according to the program. The Mexican burrowing toad, as its name suggests, spends most of the year underground, coming out only after particularly heavy rains to breed in pools of water.

    Learn about other bizarre amphibians under threat

  • Yeti crab lurks on the ocean bottom

    A Fifis  /  AP

    Named after the legendary shaggy man-beast that tromps through the snows in some of the world's tallest mountains, the Yeti crab blindly scurries about hydrothermal vents along a ridge at the bottom of the Pacific Ocean. First observed in 2005, the crab, officially named Kiwa hirsute, sports a carpet of pale yellow hairs on its arms. Scientists suspect the crab uses those hairs either to farm bacteria or to feel its way around the seafloor for food and potential mates.

    More info: Scientists to list all species on Web

  • Narwhals, the 'unicorn' whales

    Glenn Williams / Harvard Medical School

    Unicorns are purely mythical creatures, but the myths may have been inspired by narwhals. Most males and some females among the 2,200- to 3,500-pound whales sport an 8-foot-long appendage that emerges from the left side of their upper jaw. Scientists recently discovered that the elongated tooth is packed with nerve endings, making it extraordinarily sensitive. The whales may use it to determine the salinity of water and search for food. Male narwhals are also known to rub their tusks together, presumably because it gives off a unique sensation.

    More info: Mystery of 'unicorn' whale solved

  • Sucker-footed bats stick to Madagascar

    Field Museum (left); Bat Conservation Int'l (right)

    In January 2007, scientists announced the discovery of a new species of bat that uses suckers on its thumbs and hind feet to stick to broad-leafed plants such as the traveler's palm. The new species, Myzopoda schliemanni (left image), was found on the dry, western side of the African island nation of Madagascar and is closely related to another sucker-footed bat called Myzopoda aurita (right image) that lives in the humid eastern forests. Conservationists were heartened by the discovery because it suggests the bats can adapt to pioneering broad-leafed plants in deforested areas. Only about 8 percent of the island's original forest cover remains.

    Watch NBC video: What's killing all the bats?

  • Long-eared jerboa hops onto the screen

    Image: Long-eared jerboa
    ZSL

    In December 2007, conservationists released the first known footage of an endangered rodent they've nicknamed the "Mickey Mouse of the Desert." Known more formally as the long-eared jerboa, the little critter has ears about one-third larger than its head, and legs that allow for hopping like a kangaroo. The International Union for Conservation of Nature lists the species as endangered. One threat: the domestic cat.

    More info: Mongolian 'Mickey Mouse' caught on tape

  • Ligers, wholphins and grolar bears, oh my!

    Image: Liger
    TODAY show

    Every now and again, trysts between two different species result in oddball offspring that capture the public's fascination. Ligers, which are a cross between a male lion and a female tiger, were immortalized in the 2004 cult movie "Napoleon Dynamite": The main character of the 2004 cult movie, played by Jon Heder, describes it as "pretty much my favorite animal." (A real one is shown above.) Other popular hybrids include wholphins, which are a cross between false killer whales and Atlantic bottlenose dolphins; and the "grolar bear," a cross between a grizzly bear and polar bear.

    Watch NBC video of a liger
    Whale-dolphin hybrid has baby wholphin
    Hairy hybrid: Half grizzly, half polar bear

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments