GettyGeckos are known for being expert climbers, who can stick to any surface thanks to the billions of small hairy…
Geckos are known for being expert climbers, who can stick to any surface thanks to the billions of small hairy structures on the bottom of the feet. Now it turns out that the little lizards can also zip along the surface of water at high speeds to avoid predators. They can not do it for a very long time; The energy costs required are too large. But it’s amazing that they can do it at all. Researchers believe they have identified the mechanisms behind the performance, as described in a new paper in Cell Biology .
The project started when co-author Ardian Jusufi, then a postdoc at the University of California laboratory, Berkeley biophysicist Robert Full, was on vacation in Singapore during the monsoon season. One day after a big rain storm, he caught a gecko skimming across the water to fly a predator on video. The movies all amazed everyone in the lab when he showed it to them. “It was super strange and unexpected, so we must of course test this,” said co-author Jasmine Nirody, another former Full Student who now shares his time between Rockefeller University and Oxford University.
There are several creatures in nature that can go on water, but they use different mechanisms depending on their size. For example, small, lightweight water drivers are completely dependent on surface tension to keep floating while the larger, heavier basil lizards use a striking motion with the feet that create pockets of air bubbles to keep falling. The standard theoretical calculations set very strict limits for how little an animal must be for surface tension and how much it must be before the surface release mechanism is viable.
Geckos falls somewhere in between. They are too big to rely solely on surface tension and too small to generate sufficient power to run along the surface of water without sinking. And yet they can still achieve the performance at the flash speed – almost a meter per second. That’s why the Fulls team decided to investigate further.
They used laser cutters to create inlet and outlet holes in a large plastic box to make a water tank and then built two wooden ramps so their group of Asian huskekekor ( Hemidactylus Platyurus ) can easily come in and out of water. A pair of high-speed cameras were placed above and aside at right angles to capture the movement. The geckos would be placed on the ramp, and the team members would easily move their tails to make them swim away.
Geckos has developed a set of complicated mechanisms that are all for running on water.
It turns out that the geckos have developed a set of complicated mechanisms, all their own to go on water. There are two goals when you foam over water: keeps the body‘s body over the surface and forward propulsion. Firstly, gecko combines surface release and surface tension, using its unique hydrophobic skin that repels water, according to Nirody. A water drop will only sit on top of a geckos skin.
Raising their bodies over the water reduces drag, which makes it easier for geckos to push forward than if they were completely immersed. They also use a twisting motion with their bodies and tails, like swimming. “Looking at them from the top, it looks almost as if they’re just swimming very fast,” says Nirody. “And then you look at them from the side and you realize their upper body and their legs are completely away from the water, though they are still make the movement of the swimming to help drive them forward. “
To verify that surface tension actually played a role in geckoan’s surface skimming ability, the researchers added a surfactant (detergent) to the water. Surface tension occurs because water molecules tend to hold at each other (molecular adhesion), which forms a kind of supportive film to keep very light things unnecessary. Adding soap causes the molecules to lose that stickiness. Put a water cracker in soapy water and it drops because it is completely dependent on surface tension. But a basil lizard is unaffected because it completely builds on the surface.
Movements of gecko’s hind legs and hind legs like are ongoing walks on land.
Nirody et al.
Geckos combines limbs movement with body and tailbreaking.
Nirody et al.
Again, the nepkins fall somewhere in between. They did not sink, but Nirody et al . found that the addition of soap to the water reduced the coconut rate by half, probably because their bodies were much lower in the water due to reduced surface tension. “We knew that they could not maintain their entire body weight by letting themselves alone from the theoretical calculations,” said Nirody. This test showed it.
The kekos showed some interesting reactions to the soap water. About half would double their efforts to swim as quickly as possible, although their speed was severely limited. The other half, after the first strikes, just got up and planked and dropped to the bottom. Geckos can hold the breath for several minutes, so they were not in any immediate danger, even though team members saved them after about 30 seconds. “We suggested that if they can not dive away in time, rather than shake slowly from a predator, it’s best for them to just hide under the water and hold the breath,” said Nirody.
One of the objectives of this research is to improve the design of bio-inspired robots. The authors note that modeling a robot on the basil lizard would work, but it would require a lot of energy and some form of active stabilization for it to really work. A waving tail similar to geckoens can help with the latter issue and boost propulsion forward, while coating the robot with a hydrophobic material similar to the gecko skin structure can significantly reduce the draw. “Nature has so much to learn,” says Nirody. “It’s built all these amazing machines to watch and learn.”
Courtesy University of Oxford.
DOI: Current Biology 2018. 10.1016 / j.cub.2018.10.064 (To DOI).