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When choosing between life and limb, many animals willingly sacrifice their limbs. The ability to drop the appendages is known as autotomy or self-amputation. When you’re cornered, spiders lay their legs, crabs drop claws and some small rodents shed piles of skin. Some sea snails will even cut themselves to get rid of their parasite-filled bodies.
But lizards may be the best-known users of autotomy. Many lizards get rid of their wiggly tails to escape predators. This behavior confuses the predator and buys the lizard the rest of its time to escape. While losing a tail has its drawbacks—they’re useful for maneuvering, impressing mates, and storing fat—it’s better than being eaten. Many lizards have the ability to regenerate even lost tails.
Scientists have scrupulously studied this anti-predator behavior, but the structures that make it work are still puzzling. If a lizard can let go of its tail, what keeps it tied in non-life-threatening situations?
Yong-Ak Song, a biomechanical engineer at New York University in Abu Dhabi, calls it the “tail paradox”: It must be sticky and detachable at the same time. Dr. “It needs to snap off its tail quickly to survive,” Song said of the lizard. “But he also can’t easily lose his tail.”
Recently, Dr. Song and colleagues tried to resolve the paradox by examining several newly cut tails. They didn’t ask for test subjects – Dr. According to Song, the NYU Abu Dhabi campus is swarming with lizards. Using small rings attached to fishing lines, they collected several lizards of three species: two species of lizard and a desert lizard known as Schmidt’s fringed gecko.
Back in the lab, they pulled the lizards’ tails with their fingers, convincing them to perform autotomy. They filmed the resulting process at 3,000 frames per second using a high-speed camera. (The lizards soon returned to their original location.) Then the scientists pinched the writhing tails under an electron microscope.
On a microscopic scale, they could see that each fissure where the tail leaves the body is filled with mushroom-shaped pillars. When they zoomed in further, they saw each mushroom head dotted with tiny pores. The team was surprised to find that instead of the tailpieces interlocking along the fracture planes, dense pockets of microcolumns in each piece made only light contact. This made the lizard tail look like a fragile constellation of loosely interconnected segments.
However, computer modeling of tail break planes revealed that mushroom-like microstructures are adept at releasing accumulated energy. One reason is that it is filled with tiny spaces, such as tiny pores and spaces between each mushroom cap. These gaps absorb the energy of a tug, keeping the tail intact.
While these microstructures can withstand pulling, the team found that they are susceptible to shattering from a slight bending. They determined that tails were 17 times more likely to break from being bent than pulled. In slow motion videos taken by the researchers, the lizards bent their tails, cutting them cleanly in half along the plane of the fleshy fracture.
their findings, Published Thursday in the journal Science, show how these tails strike the perfect balance between robust and fragile. Dr. “It’s a good example of the Goldilocks principle applied to a model in nature,” Song said.
According to Animangsu Ghatak, a chemical engineer at the Indian Kanpur Institute of Technology, the biomechanics of this lizard’s tails resemble the sticky microstructures found on the lizard. sticky toes of geckos and tree frogs. Not included in the study, Dr. “There has to be the right balance between adhesion and separation because this allows these animals to climb steep surfaces,” said Ghatak. He added that the animals’ feet are covered with billions of tiny hairs, which are themselves mushroom-shaped heads.
Researchers believe that understanding the process that allows lizards to empty their tails could be useful for attaching prosthetics, skin grafts or bandages, and could even help robots discard broken parts.
However, Dr. Song is thrilled to finally figure out how the creatures on campus survived the predators.
“This project was purely curiosity driven,” he said. “We just wanted to know how the lizards around us cut their tails so quickly.”
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