2023-05-24 13:32:00
the invasive spider Jorō (Trichonephila clavata) made headlines due to its gigantic size, vibrant colors, and numerous webs. These can reach almost two meters in length and are strong enough to support the weight of a bird.
“It’s a creepy-looking spider that weaves giant webs on your porch,” says Andy Davis, a researcher at the University of Georgia. “She scares people. »
Originating in Asia, scientists believe Jorō spiders first arrived in North America in 2013 after stowing away as stowaways aboard a shipping container. Since then, these spiders, harmless to humans, have rapidly colonized Georgia and the bordering states. Andy Davis’ research suggests that the species may soon invade the entire eastern United States.
A new study, published in the journal Arthropodshowever, brings some good news for arachnophobes: after extensive laboratory testing, scientists have concluded that the Jorō spider is particularly fearful.
To reach this conclusion, scientists collected dozens of individuals of this species, as well as individuals of species Trichonephila clavipes, Marble spider, Diademed spider et Argiope trifasciata. The last three species are the only ones native to North America. They then tested the reactions of the arachnids to a “minor disturbance”, i.e. the sending of two rapid jets of air via a sauce baster.
Native spiders stood still for almost ninety-six seconds on average after smelling air. This reaction is known as thanatosis, or mock death. It seems to allow spiders to hide from predators. In contrast, Jorō spiders and Trichonephila clavipes waited over an hour before moving again.
“Everyone has the impression that spiders are rapidly expanding their range because they are aggressively taking over the territory of all the native spiders and outcompete them,” says Andy Davis who led the study.
On the contrary, the new research suggests that Jorō spiders are the most reserved arachnids ever observed. ” I still can not believe it. »
Still, exercising reserve can ultimately benefit spiders, making them more cautious and decreasing their chances of being eaten or killed, he adds.
When Andy Davis and his co-author, Amitesh Anerao, an undergraduate researcher, tested the Jorō spiders and the Trichonephila clavipesa related species of arachnid, perplexity quickly won over them.
“We thought we were doing it wrong because nothing was happening,” recalls Andy Davis.
Spider after spider began to take two hours each to recover from the blown air. As the building was about to close for the day, the scientists quickly had to find an alternative.
“In the end, I had to bring all the spiders home in tiny test tubes, set up little bins in my apartment to mimic the lab, and do the testing there,” Amitesh Anerao says in an email.
“The only person there was my girlfriend, so it was quite easy to create a calm environment. But having bins full of giant, palm-sized spiders certainly wasn’t the most romantic decoration for my bedroom. »
Amitesh Anerao, however, was intrigued by their long downtime. “It made me feel like we were on to something. »
Jian Zhou, a postdoctoral researcher at Argonne National Laboratory in Illinois who was not involved in the research, says “it’s quite disturbing to learn that startle reflexes last for an hour.” He adds that the study raises many other questions.
“Yes, these spiders are the most ‘reserved’ if that qualifier is defined by the time the startle reflex takes,” says Jian Zhou. who studied other orbitels. However, “what is the behavioral significance of this long startle reflex in the life of the spider”?
He wonders: “How does a spider react surprised by a juicy insect that finds itself trapped in its orbicular web? »
While Andy Davis and Amitesh Anerao believed that an aggressive nature favored the spread of the Jorō spider, especially in urban areas such as Atlanta, they now wonder if it might not be the opposite.
Perhaps this species and the Trichonephila clavipes thrive in high-stress cities because they hide instead of fleeing with every noise, movement or vibration.
To support this hypothesis, Australian researchers have shown that when another closely related arachnid, the Trichonephila plumipeslived in urban areas, he grew bigger and fathered more descendants.
“It’s too much of a coincidence that three members of this genus are so tolerant of city life,” says Andy Davis, suggesting that their discretion might be a key factor.
Maybe these little creatures will inherit the Earth after all.
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