Spiders that sacrifice their legs; crabs that shed their claws; or slugs that “decapitate themselves” to rid themselves of parasites: self-amputation is a sinisterly popular practice in the animal world when the going gets tough. However, the absolute queen of this type of practice is the lizard. Its ability to drop its tail (still in motion) and mislead predators is legendary, but until now we didn’t really know how it worked.
The tail paradox. The issue has fascinated evolutionary scientists for years, but until now it has not delved beyond its anti-predator potential. In other words, we didn’t really know how it was possible to have a fully functional tail and, from one moment to the next, lose it without causing serious problems for the animal. This is what Yong-Ak Song, a biomechanical engineer at New York University in Abu Dhabi, named in the New York Times the tail paradox: “must be simultaneously adherent and separable […] It has to detach its tail quickly in order to survive, but at the same time, it can’t lose its tail too easily.”
Remove queues in the laboratory. To find out what the mechanisms behind this ability were like, Yong-Ak Song’s team filmed with a high-speed camera (with up to 3,000 frames per second) the process by which the tails of various species of desert lizards separated from the body in a laboratory. They then analyzed these tails under an electron microscope (and returned the lizards to their natural environments).
mushroom-shaped capillaries. The first thing the researchers discovered is that there were very few vascular junction points along the sectioned portion. There were plenty of microcapillaries, but these dense pockets of vessels never touched more than lightly, making amputation quick and non-traumatic. The second finding was that these capillaries were shaped like mushrooms: by modeling them on a computer, they discovered that this shape was precisely what allowed them to cushion the blow.
The key here is that this same structure gives strength in some positions and not in others. They discovered that with certain turning movements it was up to 17 times more likely that the tail would separate from the body and that was precisely the mechanism that the lizards used to mutilate themselves in the face of danger.
What lizards can teach our prosthetics. Because therein lies the fundamental question. Beyond the curiosity of how a lizard’s tail works, researchers believe that it can help us improve how we attach prostheses, skin grafts, or bandages. It is that nature has: that it does not stop teaching us things.
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Image | Unsplash
