The Saga of the Great invasive Joro spiders that the parachute flight through the air is not over yet. A new study has found that the animals with 4-inch long legs are actually built differently, with hearts that are more resistant to the loud and busy noises of big cities.
University of Georgia researcher Andy Davis made the discovery while conducting cardiac stress tests on joro spiders and their cousin, the golden silk spider. The study, published Monday in Physiological Entomology, found that the species know how to relax and stay calm when faced with situations that cause their heart rate to increase.
The Joro spider, also known as Trichonephila clavata, “is known to build its webs not only in natural green spaces but also in towns and villages, often on buildings and human dwellings,” the study says. “The stress responses of Trichonephila spiders could be characterized as ‘balanced,’ which could explain their ability to live in habitats with frequent disturbances.”
Davis and his team studied the physiological responses of Joro spiders and golden silk spiders and compared them with those of another pair of similarly sized but related species, namely garden spiders and banded garden spiders.
The researchers recorded the arachnids’ baseline heart rate while they were resting and inactive, and then recorded their heart rate after holding them under electronic sensors for 10 minutes.
Alex Sanz/AP
“When exposed to the new stress, the heart rate of all spider species increased, an expected response that other spider researchers have also observed,” the study says. “However, there were differences between species in the magnitude of this increase and in how the responses developed over the 10-minute period.”
The garden spiders, both of which belong to the genus Argiope, showed “clear periods of fluctuation during restraint” and even resisted the restraints, the researchers said. Joro spiders and their golden silk relatives, on the other hand, were “less variable and more consistent.” They were also observed to enter a state of thanatosis for more than an hour after exposure to stressors, meaning they essentially froze during that time.
The tests “are beginning to paint a picture of how the invasive Joro spider and its cousin, the golden silk spider, uniquely tolerate novel stressors. This may explain their ability to colonize man-made landscapes,” the researchers said. They note that other spider species in their family lineage may also share this trait, but this requires further investigation.
Joro spiders have been making headlines for years as they continue to spread up the East Coast. Originally from Asia, the spiders are believed to have first been introduced to northern Georgia around 2010. Since then, they have been found in nearly a dozen other states. In December, Davis told the New York Times that New York is “right in the middle of where they like to hang out.” It has been predicted that they could show up in the New York tri-state area this summer, although there have been no reports of them.
Dave Coyle/Clemson University
“They don’t seem to have a problem living in the city,” he told the newspaper, adding that they have been seen hanging around street lamps and telephone poles where “normal spiders wouldn’t even hang out.”
While the latest findings do not prove conclusively that the spiders’ relaxed behavior is the reason for their “affinity for urban environments,” the study says, and further research is needed, they do reinforce Davis’ research from February, which also found that joro spiders are not necessarily bothered by the increased noise and vibrations that come with city life.
“These Joro webs are everywhere in the fall, even right next to busy roads, and the spiders seem to be able to survive there. For some reason, these spiders seem to be urban tolerant,” Davis said of his previous research.
Alexa Schultz, UGA graduate student and co-author of the study, agreed, saying, “It looks like Joro spiders aren’t afraid to build a web under a traffic light or in a place where you wouldn’t expect to find a spider.”
But don’t worry – although the spiders are poisonous, they pose no danger to humans. However, they may increase your heart rate more than you increase your pet’s.
