Ever wonder how fleas jump?

In 1967, a scientist by the name of Henry Bennet-Clark discovered that fleas store the energy needed to catapult themselves into the air in a pad made of the unique 'elastic' protein resilin. However, in the intervening years, debate raged about exactly how fleas harness this explosive energy. Scientists came up with competing hypotheses, but it wasn't until recently that the technology necessary to record and analyse the data became available.

Using high-speed recording equipment and sophisticated mathematical models, Professor Malcolm Burrows and Dr Gregory Sutton from the University's Department of Zoology, were able to prove that fleas use their toes to push off and propel themselves into the air, resolving the 44 year old mystery. Their findings are published February 10, in the Journal of Experimental Biology.

"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. 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. 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?

Analysing the movies, the scientists 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, preventing it from getting a good grip to push off.

Sutton and Burrows suspected that the insects push down through the tibia (shin) onto the tarsus (toe). Using a mathematical model that could reproduce the flea's trajectory, the scientists were able to confirm that the insects transmit the force from the spring in the thorax through leg segments acting as levers to push down on the tarsus (toe), solving the 44 year old mystery

Have you ever wondered what happened that snakes lost their legs?

Some, if not all, snakes used to have legs, and now new research suggests snakes lost their limbs by growing them more slowly or for a shorter period of time.

The research, outlined in the latest issue of the Journal of Vertebrate Paleontology, strengthens the belief that snakes evolved from a lizard that either burrowed on land or swam in the ocean.

In either case, its legs must have become less useful as the animal evolved over time.

"If something is not useful it can regress without any impact on the (animal's) survival, or regression can even be positive, as for here if the leg was disturbing a kind of locomotion, like for burrowing snakes or swimming snakes," lead author Alexandra Houssaye told Discovery News.

For the study, Houssaye, from the National Museum of Natural History in Paris, and her colleagues analyzed a fossil snake named Eupodophis descouensi. The prehistoric snake lived during the Cretaceous Period in what is now Lebanon.

To better examine the snake, the scientists used a new imagining technique called synchrotron-radiation computed laminography (SRCL). With an intense, high-energy beam of X-rays, the SRCL deeply penetrated the fossil as the researchers rotated it. The result was thousands of two-dimensional images that were later compiled into a three-dimensional model of the ancient snake's hips and ultra tiny .8-inch legs.

"Synchrotrons are enormous machines and allow us to see microscopic details in fossils invisible to any other techniques without damage to these invaluable specimens," said co-author Paul Tafforeau from the European Synchrotron Radiation Facility.

The new 3-D model determined that Eupodophis, in its lifetime, had two small regressed hind limbs and no front limbs. The leg visible to the researchers was bent at the knee, possessing four anklebones but no foot or toe bones. The high tech imaging further showed that the internal architecture of the leg bones strongly resembled that of modern terrestrial lizard legs.

Houssaye said "the legs were very regressed" in this snake, which she added is not the world's oldest snake, but it comes pretty close.

"The oldest snake remains are dated to 112 to 94 million years ago, and this snake is dated to around 90 million years ago," she explained.

Yet another snake from the same time period, Najash rionegrina, is also thought to have had two small rear legs, strengthening the theory that snakes once had legs and evolved from a lizard with limbs. Hussam Zaher of the University of Sao Paolo in Brazil, and a colleague found Najash (which means "snake" in Hebrew) at the Rio Negro province ofArgentina.

Najash retained a sacrum, a bony feature that supported the pelvis. Zaher believes this feature was lost as snakes evolved from lizards. The fossil snake from Argentina is also thought to have lived on land, since it was found in what was once a terrestrial environment. Zaher said its anatomy suggests this snake lived in burrows.

Houssaye, however, does not think the case is yet closed as to whether or not snakes evolved from a marine or land-based lizard.

"The question of snake origin should not be resolved in the next 10 years," Houssaye said.

She is, however, hopeful that all of the separate teams working on this puzzle can one day pinpoint what species was the common ancestor of all snakes.