44-year-old mystery of how fleas jump resolved

Fleas jump by pushing off with the toes instead of knees

2011-02-10

(Press-News.org) If you thought that we know everything about how the flea jumps, think again. In 1967, Henry Bennet-Clark discovered that fleas store the energy needed to catapult themselves into the air in an elastic pad made of resilin. However, in the intervening years debate raged about exactly how fleas harness this explosive energy. Bennet-Clark and Miriam Rothschild came up with competing hypotheses, but neither had access to the high speed recording equipment that could resolve the problem. Turn the clock forward to Malcolm Burrows' Cambridge lab in 2010. 'We were always very puzzled by this debate because we'd read the papers and both Henry and Miriam put a lot of evidence for their hypotheses in place and their data were consistent with each other but we couldn't understand why the debate hadn't been settled,' says Burrows' postdoc, Gregory Sutton. He adds, 'We had a serendipitous set of hedgehog fleas show up so we figured we'd take a crack at it and try to answer the question'. Filming leaping fleas with a high-speed camera, Sutton and Burrows found that fleas push off with their toes (tarsus) and publish their discovery in The Journal of Experimental Biology at http://jeb.biologists.org/cgi/content/abstract/214/5/836.

'We were concerned about how difficult it would be to make the movies because we are used to filming locusts, which are much bigger than fleas,' admits Sutton, but he and Burrows realised that the fleas stayed perfectly still in the dark and only jumped when the lights went on. Focusing the camera on the stationary insects in low light, the duo successfully filmed 51 jumps from 10 animals; and this was when they got their first clue as to how the insects jump.

In the majority of the jumps, two parts of the flea's complicated leg – the tarsus (toe) and trochanter (knee)– were in contact with the ground for the push off, but in 10% of the jumps, only the tarsus (toe) touched the ground. Sutton explains that Rothschild had suggested that fleas push off with the trochanter (knee), but if 10% of the jumps didn't use the trochanter (knee) was it really necessary, or were the fleas using two mechanisms to get airborne?

Burrows and Sutton needed more evidence. Analysing the movies, the duo could see that the insects continued accelerating during take-off, even when the trochanter (knee) was no longer pushing down. And the insects that jumped without using the trochanter (knee) accelerated in exactly the same way as the insects that jumped using the trochanter (knee) and tarsus (toe). Also, when Burrows and Sutton looked at the flea's leg with scanning electron microscopy, the tibia (shin) and tarsus (toe) were equipped with gripping claws, but the trochanter (knee) was completely smooth, so it couldn't get a good grip to push off. Sutton and Burrows suspected that the insects push down through the tibia (shin) onto the tarsus (toe), as Bennet-Clark had suggested, but the team needed one more line of evidence to clinch the argument: a mathematical model that could reproduce the flea's trajectory.

'I looked at the simplest way to represent both models,' explains Sutton. Building Rothschild's model as a simple mass attached to a spring pushing down through the trochanter (knee) and Bennet-Clark's model as a spring transmitting the spring's force through a system of levers pushing on the tarsus (toe), Sutton generated the equations that could be used to calculate the insect's trajectory. Then he compared the results from his calculations with the movies to see how well they agreed.

Both models correctly predicted the insect's take-off velocity at 1.35m/s, but then the Rothschild model began to go wrong. It predicted that the insect's acceleration peaked at a colossal 22,000m/s2 (2200g), whereas the acceleration of the insects in the movies only peaked at 1500m/s2 (150g). However, Sutton's calculations based on the Bennet-Clark lever model worked perfectly, accurately predicting the insect's trajectory and acceleration pattern.

So Sutton and Burrows have finally settled the argument and resolved how fleas jump. The insects transmit the force from the spring in the thorax through leg segments acting as levers to push down on the tarsus (toe) and launch the 0.7mg animals at speeds as high as 1.9m/s.

INFORMATION:

This work was funded by the Human Frontiers Science Program and the Marshall Sherfield Commission.

IF REPORTING ON THIS STORY, PLEASE MENTION THE JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org/cgi/content/abstract/214/5/836

REFERENCE: Sutton, G. P. and Burrows, M. (2011). Biomechanics of jumping in the flea. J. Exp. Biol. 214, 836-847.

This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT permissions@biologists.com

THIS ARTICLE IS EMBARGOED UNTIL THURSDAY, 10 February 2011, 00.15 HRS EST (05:15 HRS GMT)

[Attachments] See images for this press release:

ELSE PRESS RELEASES FROM THIS DATE:

New research helps explain how progesterone preventspreterm birth

2011-02-10

SAN FRANCISCO, FEB. 10, 2011 -- Research presented today at the 31st Annual meeting of the Society for Maternal-Fetal Medicine (SMFM) -- The Pregnancy Meeting™ has found that three proteins known as XIAP, BID, and Bcl-2 are responsible in part for the success of progesterone treatments in the prevention of preterm labor. They may also play an important role in triggering normal labor. The proteins prevent preterm birth by hindering apoptosis – the normal, orderly death of cells -- in the fetal membranes. Stronger, thicker fetal membranes are less likely to rupture ...

Study finds women used 30 percent less analgesia during labor when self-administered

2011-02-10

SAN FRANCISCO (February 10, 2011) — In a study to be presented today at the Society for Maternal-Fetal Medicine's (SMFM) annual meeting, The Pregnancy Meeting ™, in San Francisco, researchers will present findings that show that when women administer their own patient-controlled epidural analgesia (PCEA) instead of getting a continuous epidural infusion (CEI) they used less analgesic, but reported similar levels of satisfaction. Women often receive a continuous epidural infusion of analgesic during labor. This can lead to prolonged labor and an increase in assisted vaginal ...

When first-time mothers are induced, breaking the amniotic membrane shortens delivery time

2011-02-10

SAN FRANCISCO (February 10, 2011) — In a study to be presented today at the Society for Maternal-Fetal Medicine's (SMFM) annual meeting, The Pregnancy Meeting ™, in San Francisco, researchers will present findings that show that by performing an amniotomy on first time mothers in situations when labor has to be induced, that delivery time can be shortened by more than 10 percent. There are many reasons that labor may need to be induced after a woman's due date. Today's study looked at whether or not performing an amniotomy early on in the labor process would shorten ...

Long- and short-sleeved physician workwear receive same amount of bacterial and MRSA contamination

2011-02-10

Governmental agencies in the United Kingdom recently instituted guidelines banning physicians' white coats and the wearing of long-sleeved garments to decrease the transmission of bacteria within hospitals due to the belief that cuffs of long-sleeved shirts carry more bacteria. However, a new study published today in the Journal of Hospital Medicine shows that after an eight-hour day, there is no difference in contamination of long- and short-sleeved shirts, or on the skin at the wearers' wrists. A group of researchers from the University of Colorado, USA, decided to ...

Cancer breakthrough to prevent heart failure and increase survival rates

2011-02-10

A breakthrough by scientists at Queen's University Belfast could help reduce heart failure in cancer patients around the world, and ultimately increase survival rates. Scientists at Queen's Centre for Vision and Vascular Science have discovered the role of an enzyme which, when a patient receives chemotherapy, can cause life-threatening damage to the heart. This has, until now, restricted the amount of chemotherapy doses a patient can receive; but while protecting the heart, this dilutes the chemotherapy's effectiveness in destroying cancerous tumours. By identifying ...

Think manager, think male? Impact of gender in sport administration hiring

2011-02-10

The "glass ceiling" for women administrators in college athletics may be cracked, but is not completely broken, according to a new study co-authored by a North Carolina State University researcher. Results of the study, which surveyed athletic administrators at universities across the country to determine how, and if, gender roles made a difference in hiring practices, may disappoint those who think double standards for women have been relegated to the past. Dr. Heidi Grappendorf, assistant professor of parks, recreation and tourism management at NC State, and colleagues ...

The Maloof High Ollie Challenge Finals Set for Las Vegas Feb 14-15 During MAGIC - Skaters Attempt to Break Guinness World Record

2011-02-10

Maloof Skateboarding will host the final round of its Maloof High Ollie Challenge on February 14-15 in Las Vegas during MAGIC, the most influential event in the business of fashion. Pro Skaters Torey Pudwill, Corey Duffel, Johnny Layton, Levi Brown, Garrett Hill, Darren Harper and Steve Nesser will compete against 14 skaters who won regional contests at skate shops across the country, the winner of an online video contest, as well as top amateur skaters Luis Tolentino, Anthony Schultz, Kechaud Johnson, Austyn Gillette and Aldrin Garcia. The winner will take home $10,000 ...

Plagiarisma.Net Introduces Google Books Plagiarism Checker

2011-02-10

The owner of Plagiarisma.Net noticed that most students could copy and paste any text coming from the Google books because they are not included in most of plagiarism tools available in the internet. This theft and copyright violation has been rampant because most software is not able to detect the copied text. "Well, it is high time that we push on adding more script to existing plagiarism checker tools and help students and other writers polish their talents by writing their articles and their thesis in their own words and understanding. We need to raise awareness about ...

Breaking Environmental News -- Planet Sludge: Tens of Millions of Abandoned Gas and Oil Wells Foretell Environmental Disaster of Unprecedented Proportions

2011-02-10

A three-month EcoHearth.com investigation has revealed a developing environmental catastrophe that almost no one is paying attention to and which gravely threatens ecosystems worldwide. There are at minimum 2.5 million abandoned oil and gas wells, none permanently capped, littering the US, and an estimated 20-30 million globally. There is no known technology for securely sealing these tens of millions of abandoned wells. Many--likely hundreds of thousands--are already hemorrhaging oil, brine and greenhouse gases into the environment. Habitats are being fundamentally ...

Poly Tarps Bring Hope in Wake of Hurricane Forecast

2011-02-10

When the 2011 Hurricane forecast was announced, the people in the gulf states were not too happy. The leading U.S. tarps supplier is trying to lessen the blow with preparedness. The tarps company has increased if poly tarps inventory by 20% and anticipates another re-stock of the high demand poly tarp cover. The natural disasters that are often associated with unusual weather changes are happening all too often these days. Families are left devastated as they lose their homes and sometimes their entire families to these tragic occurrences. Hurricanes cause oil spills ...

UK study shows there is less stigma against LGBTQ people than you might think, but people with mental health problems continue to experience higher levels of stigma

44-year-old mystery of how fleas jump resolved

ELSE PRESS RELEASES FROM THIS DATE:

LAST 30 PRESS RELEASES: