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Tangle-web spiders are eight-legged engineers, making silk pulleys to catch oversized prey like lizards or even small mammals walking on the ground below.
Until now, scientists weren’t sure exactly how arachnids were able to capture such heavy victims. For the first time, researchers have analyzed spider construction techniques and silk construction to trap and lift heavy animals.
It turns out that the spiders actively “tuned” their silk mechanisms once the prey had been caught, tying pre-stretched wires into pulleys to maximize their lifting power and raise prey much heavier than the arachnids themselves. , the researchers reported in a new study.
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Spider silk is very good at dispersing energy; when an insect flies in a web, the energy of its struggles is absorbed and dissipated through the network of joined threads. Silk is also elastic, which allows it to store and amplify energy, much like the string of a bow that is stretched and then released to shoot an arrow.
For the study, scientists wondered how tangled spiders could use the silk elastic to do their heavy lifting, whenever their sticky trapping wires caught something too bulky for the spider to pull out of the way. ground.
There are over 2,200 species of entangled spiders described in the Theridiidae family (also known as spider web weavers). They live all over the world and are known for their dense, irregularly shaped webs, according to the Biodiversity Database. Encyclopedia of Life (EOL). For the researchers’ experiments, they worked with two species of tangle-web – Steatoda paykulliana and Steatoda triangulosa – and instructed the spiders to raise live cockroaches spotted with orange (Blaptica dubia). Spiders weighed 0.007 ounces (0.22 grams) at most, and the heaviest cockroaches weighed almost three times as much as 0.02 ounces (0.56 g).
“The trap changes”
During the experiments, scientists observed the spiders as they built their snares, hanging special fibers studded with sticky glue to both trap prey and signal the spider when something was caught. If the unlucky victim is a small insect, that thread may be enough to lift it, said lead author of the study Gabriele Greco, postdoctoral researcher at the University’s Laboratory of Bio-Inspired, Bionic, Nano, Metamaterials Mechanics at the University. from Trento to Italy.
But if the prey is too big for the spider to shoot using the power of its own paws, “that’s when the trap changes,” Greco told Live Science. “The spider is getting involved too.”
No longer a passive observer, the spider then begins to produce hypertension threads – silk fibers that the spider stretches as it anchors one end to the web and attaches the other to the trapped prey. When the threads relax, they release their stored energy to gradually increase the animal’s weight, and the spider does this over and over again until the prey is at the desired height, Greco explained. In the experiments, the spiders lifted the large cockroaches up to eight centimeters off the ground and their fastest lifting speed was about 0.004 inches (0.01 cm) per second, the researchers reported.
The study authors also described four different types of silk that spiders used to build the web, each with a specific function. There were two types of support wires, each produced by a different gland; “trapping” threads, covered with sticky droplets; and finally, a cement-like silk connecting the threads together. The spider then produced a fifth type of silk to bind and immobilize its prey, Greco said.
“The spider is a perfect silk factory, it produces multifunctional materials in less than milliseconds – at least five different materials,” he added.
Another type of arachnid – the triangular weaver spider (Tengellidae cavatus) – also takes advantage of the ability of silk to store and release energy; he uses his silk to make stretchy slings that launch the spider much farther than it could travel by jumping, Live Science reported in 2019.
But researchers still do not know much about the elasticity of spider silk, such as how much the silk can relax and stretch again. Calculating this limit would help scientists understand how much a spider could stretch the tension threads, which must also withstand the struggles of a captured animal without cracking or becoming limp.
“These are just the first glimpses in this direction,” Greco said.
The results were published online Feb. 3 in the Royal Society Interface Journal.
Originally posted on Live Science.
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