Deinopis spiders have eight eyes, but the two massive forward-facing orbs are by far the most impressive.

The deinopis spider can only impress, with her huge eyes, monstrous orbs that allow it to spot its prey in the dark.

This nocturnal arachnid is also distinguished by its extraordinary hearing. New study says spider can hear a surprising range of sounds over 1.82 distance meter, thanks to the sensory organs located on its legs.

Native to the Southeastern United States, these araneomorphic spiders of the Deinopidae family hunt by swaying, then move backwards to capture aerial prey in their web.

Curious as to how spiders could accomplish a feat of such agility, Jay Stafstrom, postdoctoral researcher in neurobiology at Cornell University, conducted an experiment in which he covered the eyes of spiders with a piece of silicone. Curiously, blindfolded predators could still catch flying insects, which suggests that they could also hear them.

Spiders don't have ears, in the conventional sense of the term. But more and more evidence indicates that some spiders – like jumping spiders, dolomedes and deinopis – can hear through nerve receptors located on their legs. Receivers work like ears, picking up sound waves and communicating impulses to the brain. The ability of spiders to sense the vibrations produced by the legs of their prey on their webs is well known., but it is not considered auditory.

Which is all the more impressive when it comes to deinopis spiders, this is how well they can hear, indicates Stafstrom, whose study was published in the journal Current Biology. Unlike some species (like jumping spiders) who cannot hear high frequency sounds, deinopis spiders can detect both low frequency sounds (the beating of insect wings) and the high frequency chirping of birds, their main predators.

Discovery of such advanced hearing could help scientists learn more about the evolution of the sense of hearing, as Sen Sivalinghem explains, sensory biologist at the University of Toronto, who did not take part in the study.

According to a new study, the deinopis spiders first weave their web, then catch flying insects by swinging quickly backwards.

"Understanding how sensory information is processed in the brains of relatively less complex animals with fewer neurons – and how it affects their behavior – can give us information on how all types of brains work ”, he says. "Including ours. »

As part of a new laboratory experiment, Stafstrom and his colleagues inserted tiny electrodes into the brains of spiders as well as disembodied legs, that can react to sounds for up to an hour after being muted. Scientists suspected that the metatarsal organs, located near the end of each leg in the spider and responsible for detecting vibrations, were also used to hear.

The scientists then played sounds at a distance of about 1.80 metre. Analyzes revealed that spiders' brains and metatarsal organs were activated when exposed to low and high frequency sounds. When Scientists Disabled Spiders' Metatarsal Organs, arachnids did not react as strongly to sounds, which suggests that the organs act like eardrums.

To confirm these results, the team also conducted experiments on spiders in their natural habitat in Gainesville, in Florida, playing the same sounds at a distance of 1.80 meter at night.

The results were the same : spiders cast their nets when they hear low frequencies that mimic the wings of insects, and remained still when hearing high frequency sounds, which could have indicated the presence of a predator. These findings reinforced what the researchers had already found : spiders can actually hear and don't just react to vibrations in their web.

"One of the really exciting aspects of this study is the combination of behavioral experiments and neurophysiological work", Sivalinghem declares.

"It is notoriously difficult to record brain activity in spiders", he adds, meaning that "we know very little about how sensory information is processed and what information is important to spiders. »

Source: https://www.nationalgeographic.fr/animaux/2020/10/comment-cette-araignee-peut-elle-entendre-sans-oreilles

Spider, Deinopidae, Arachnid, Deinopis

World news – FR – How can this spider hear… without ears ?

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