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Infected zombie spiders are forced to create incubation chambers for their parasitic overlords

Annelosimus eximius spider.
Image: Philippe Fernandez-Fournier

Parasites that control the behavior of their hosts for their own benefit are a well-documented natural phenomenon, but the discovery of a previously unknown connection between the parasitic wasp and the social spider is particularly frustrating.

Hijacking the brain of unsuspecting hosts is what some organisms do, usually for reproductive purposes. Notable examples include a fungus that controls the actions of carpenter ants, a unicellular parasite that makes cat urine smell irresistible to rodents, and a worm that causes infected fish to perform a complex dance.

Another parasitic attitude, discovered by scientists from the University of British Columbia, can now be added to this list – and this is one of the most unpleasant of all that we have seen, both in terms of its complexity and with ill will. In a new study published today in Ecological Entomology, lead author Philip Fernandez-Fournier describes how Zatypota parasitic wasp species use and abuse social Annelosimus eximius spider, first using it as an escape machine, and then forcing it to build an incubation chamber. Oh, and then he eats the spider.

Fernandez-Fournier accidentally stumbled upon a discovery in the Ecuadorian Amazon, studying various parasites living in nests. A. eximiusThese arachnids are called social spiders, because they live in large colonies, work together to capture prey, divide parental responsibilities, and rarely go beyond the cozy borders of their communal nests in the form of a basket.

The larva of Zatypota, clinging to its owner, Annelosimus eximius spider.
Image: Philippe Fernandez-Fournier

These spiders are tough in their behavior, so Fernandez-Fournier noticed that some of these spiders, which were infected with a parasitic larva, deviated by about one or two feet from the colony. This observation was strange and rare for himself, but the UBC scientist also observed how these same spiders began to rotate the fabrics of tightly wound silk and pieces of foliage.

“It was very strange because they usually don’t do that, so I started taking notes,” Fernandez-Fournier said in a statement.

It is curious that he returned the cocoon-web to the laboratory. When he threw them on the shock, he saw the inner fish. Realizing that he was on something, Fernandez-Fournier and his team investigated further, uncovering the completely undocumented interaction between the two species.

Here's how it works: adult woman Zatypota wasps lay an egg on the belly Annelosimus eximius spider. After the larvae hatch, it attaches to the spider and feeds on its blood. The larva becomes larger and begins to absorb most of the spider's body. In the end, the spider enters a state of "zombification" in which it no longer behaves like its normal "me." Under the influence of the larva, the spider leaves its colony and sets itself the task of building a cocoon web. As soon as this compulsory building task is completed, the spiders remain motionless, allowing the larva to finish the job of killing and consuming its master. Focused, the larva merges into a web cocoon, which it uses as an incubator for its next stage of germination. In about 9-11 days, a perfectly mature wasp emerges from the cocoon. The cycle begins anew, unfortunately, for the next eight-legged victim.

The strategy, according to researchers, is unique in that parasitoid wasps were previously documented only for the extraction of single spiders.

“But this behavior modification is so hardcore,” said Samantha Strauss, co-author of the study, in a statement. “The wasp completely absorbs the behavior of the spider and the brain and makes it something that it will never do, for example, leave its nest and deploy a completely different structure. This is very dangerous for these tiny spiders.

To which the Ostrich added: “We think that the wasps are aimed at these social spiders, because they provide a large, stable colony of hosts and a source of food. We also found that the larger the colony of spiders, the more likely it is that these wasps will target it. ”

From the point of view of how a wasp larva weaved its hypnotizing spell, the researchers theorize that it injects a brain-altering hormone into a spider. This hormone either deceives the spider, thinking that it is at a different stage of life, or works as a signal that causes the spider to escape from its colony. But this is only speculation.

Fernandez-Fournier and Straus would now like to return to the Ecuadorian forest to learn more about these devilish wasps and their owners. In particular, they would like to know whether the wasps are constantly attacking the same spider colonies, and if so, how this behavior works as an advantage.

[Ecological Entomology]

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