March 29, 2024

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The lizard tail paradox is finally resolved

The lizard tail paradox is finally resolved

Lizard (Horacio Patron)

When forced to choose between their life and a limb, many animals are willing to sacrifice their limbs. The ability to get rid of appendages is known as self-cutting, or self amputation. When cornered, spiders shed their legs, crabs drop their claws, and some small rodents shed bits of their skin. Some marine mollusks even decapitate themselves to separate themselves from their parasite-infested bodies.

However, Lizards are probably the creatures best known for resorting to self-conquest. To avoid predators, Many lizards drop their tails, which continue to move even after the fact. This behavior confuses the predator, giving the lizard enough time to escape. Although losing the tail has its downsides – useful for maneuvering, impressing mates, and storing fat – it is preferable to eat it. Many lizards are able to replenish their lost tails.

Scientists have carefully studied this defense system against predation, but the structures that shape its operation are unclear. If a lizard can shed its tail in an instant, what keeps it in place in non-life-threatening situations?

Young Ak Sung, a biomechanical engineer at New York University in Abu Dhabi, calls this The “glue paradox”: It must be adherent and removable at the same time. “It must be able to separate from its tail quickly to survive,” Song said of the lizard. “But at the same time, the tail can’t easily slip off.”

Song and colleagues recently set out to solve this paradox Analyze many newly anchored tails. They did not lack research topics: according to Song, the Abu Dhabi campus is teeming with geckos. Using small clips attached to fishing poles, they collected several lizards of three species: two types of geckos and a desert lizard known as the Schmidt-toed lizard.

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Once in the lab, they pulled the lizards’ tails with their fingers to convince them to resort to self-opening. They filmed the resulting process at 3,000 frames per second with a high-speed camera. (Soon after, the lizards were returned to where they were found.) Then the scholars They put the still writhing tails under the electron microscope.

On a microscopic scale, they were able to see that each fracture where the tail separated from the body was studded with mushroom-shaped plumes. Zooming in, they saw that each mushroom cap had multiple small pores. The team was surprised to find out The tail segments did not intertwine along the fracture regions, instead, the dense arrays of micropyles in each segment appeared to barely touch. This made the lizard’s tail look like a fragile constellation of not closely connected segments.

However, computer modeling of the rifting zones in the tail revealed that the mushroom-shaped microstructures were able to release the suppressed energy. One reason for this is that they are full of tiny gaps, like pores and tiny spaces between each cap of mushrooms. These voids absorb the energy generated by the drag, allowing the tail to remain intact.

While these delicate structures can withstand stress, the team found that they are prone to detachment by slight torsion. they decided that Tails were 17 times more likely to break when bent than when pulled. In the slow motion videos captured by the researchers, the lizards twisted their tails to snap them neatly in two along the area of ​​the stromal break.

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Their findings were published Thursday in the scientific journal to knowExplain how these queues Strike the perfect balance between hardness and brittleness. “It’s a beautiful example of the Goldilocks principle applied to a model in nature,” Song said.

According to Animangsu Ghatak, a chemical engineer at the Indian Institute of Technology in Kanpur, the biomechanics of these lizard’s tails are reminiscent of the sticky micro-structures seen on the toes of geckos and tree frogs. “They have to have the right balance between sticking and detaching, because that allows these animals to climb up very steep surfaces,” explained Gatak, who was not involved in the study. He added that the animals’ feet were covered with billions of tiny hairs, which in turn consist of mushroom-like caps.

Researchers consider that Understanding the process that allows lizards to shed their tails may be useful for attaching prosthetics, skin grafts, or bandages, and may also help robots cut away broken parts..

However, Song is more excited to finally understand how the creatures on campus escape predators.

“This project was entirely based on curiosity,” he said. “We just wanted to know how the lizards around us cut their tails so quickly.”

© New York Times 2022