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WPool An involuntary victim trips into a spider web, the Arachnid host generally welcomes the unhappy creature in his house by packing it in silk and piercing it with fangs full of venom. In most cases, this venom is sufficient to paralyze completely, and sometimes even kill the prey. But for insects that are captured by rare Ulobridae spiders, they are not poisonous fangs they need to worry. This is what is prepared in the guts of these spiders.
“I found this reference of this very old newspaper saying that this family of spiders had not come and that I said to myself what?” Wait a second. I thought that all the spiders were poisonous, ”explains Giulia Zancolli, an evolving biologist at the University of Lausanne. “So, I then started to dig.”
She came across a drawing in an article from 1931, which showed that the heads of these spiders do not contain the venom glands that most species of spiders are doing. “But it was really the only data available,” she says. So she decided to check for herself.
Zancolli and his colleagues turned their attention to a species with UloBoridae family called Ulobora Plumipesor the spider of lace weavers with feathered legs. A delicate small spider, U. plumipes Envelops its prey in hundreds of silk feet, wrapped wider than most spiders. After mummifying its prey, the spider then vomits on the tight beam.
When Zancolli and his colleagues dissected the heads of the spiders, they found large prominent muscles but no venom glands. And when they looked closely at the hooks of the spiders, they found that they even lacked an opening through which the venom could be ejected, providing additional evidence that these spiders had lost their venom glands during evolution.
After mummifying its prey, the spider then vomits on the tight beam.
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“As far as I know, no other group of spiders has lost its venom glands,” said Ronald Jenner, an evolving biologist at the Natural History Museum in London who was not involved in the study.
Scientists wanted to determine if another organ in the spider body could perhaps contain the missing venom. They therefore looked for genes of active venom in its other parts, such as its reproductive organs, its silk producing glands and its intestine. And now, the intestine seemed to contain genes that could code for venom -type substances.
To confirm that U. PlumipesThe intestinal secretions were indeed toxic, they injected them into fruit flies. By way of comparison, they also injected flies with secretions from the intestine of a kind of venomous spider. The two secretion sets killed flies, suggesting that U. Plumipes Use its toxic digestive fluids to participate in killing, but that these intestinal secretions are common among spiders. In other words, the venom of croc used by other spiders has probably not migrated to the intestine, but rather U. Plumipes learned to use preexisting intestine secretions in a new way. Scientists have recently published their results in BMC biology.
“The venom system is expensive … It costs metabolic energy to make venom and to maintain this system,” explains Jenner. “Thus, in these spiders, the loss of the venom system means that they should have evolved a different way of immobilizing prey.”
The secret of immobilization for U. Plumipes lies in the packaging of extensive silk and in the equally extended propagation of the liquid. The spider makes “a burrito” of his prey, explains Jenner. Then, it regurgitates the toxic digestive fluids on the entire packaging, which kills both prey and then continues to dissolve its tissues. “A spider only takes liquid foods so that it can go up the digestive broth caused by the regurgitation of digestive fluids,” explains Jenner.
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Usually, spiders only throw toxins specifically in bite wounds, so that if the venom has not already killed prey, vomit will be. “It is a preserved feature of having such powerful digestive fluids, but the idea is that these spiders have not come to somehow reused it to use it for predation,” explains Zancolli.
As for why the UloBoridae The family of spiders as a whole lost the glands of venom in their heads, Jenner thinks that it is because they no longer needed venom to eliminate their prey. “I think they have become Burrito manufacturers in silk so experts as they no longer need venom for immobilization,” he said. Some sea snakes have evolved along a similar trajectory, losing all the organs involved in the poisoning of prey when they started to feed on fish eggs, which do not require capture or immobilization.
As a next step in research, Jenner thinks that scientists should examine the expression of certain key toxin or venom genes through the phylogenetic spiders, and also through other arachnids. “It was very interesting to see how many toxins are expressed in the intestine” of U. Puidesaid Jenner. But are these toxins also present in other spiders?
Anyway, in time, spiders seem to have evolved several ways to enjoy their liquid lunch.
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Main image: Netha Hussain / Wikimedia Commons
