The saga of the great Invasive Joro Spiders That parachute in the air isn’t over yet. A new study has found that the four-inch-long-legged creatures are actually built differently, with hearts that can withstand the loud, animated noises of big cities.
Andy Davis, a researcher at the University of Georgia, made the discovery while conducting cardiac stress tests on Joro spiders and their cousin, the golden silk spider. The research, published Monday in Physiological Entomology, found that the species knows how to relax and stay calm when placed in situations where their heart rate increases.
The Joro spider, also known as Trichonephila clavata, “is known to spin webs not only in natural green spaces, but also in cities and towns, often on buildings and human dwellings,” the study says. “The stress responses of Trichonephila spiders could be described as ‘balanced,’ which could explain their ability to live in frequently disturbed habitats.”
Davis and his team evaluated the physiological responses of Joro spiders and golden silk spiders and compared them to those of another pair of similarly sized species that are related to each other, garden spiders and banded garden spiders.
The researchers recorded the arachnids’ baseline heart rates while they were resting and inactive, then recorded their heart rates after immobilizing them under electronic sensors for 10 minutes.
Alex Sanz / AP
“When subjected to this novel restraint stress, the heart rate of all spider species increased, which is an expected response that other researchers have noted,” the study says. “However, there are differences between species in the magnitude of this increase and how the responses evolve over the 10-minute period.”
The garden spiders, both of which belong to the genus Argiope, showed “distinct periods of fluctuations during restraint” and were even found to struggle against the restraints, the researchers said. The Joro spiders and their golden silk cousins, on the other hand, were “less variable and more uniform.” They were also observed entering a state of thanatosis for more than an hour after stressors, meaning they essentially froze during that period.
The tests “begin to paint a picture of how the invasive Joro spider and its cousin, the golden silk spider, have a unique way of tolerating novel stressors, which may underlie their ability to occupy anthropogenic landscapes,” the researchers said, noting that other spider species in their family lineage may share this trait, although this would require further research.
Joro spiders have been making headlines for years as they continue to spread across the East Coast. Native to Asia, the spiders were first thought to have been introduced to northern Georgia around 2010. They have since been discovered 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 be.” There are predictions that they could reappear in the New York tri-state area this summer, though there have been no reports of that happening.
Dave Coyle/Clemson University
“They seem to be doing well in the city,” he told the newspaper, adding that they have been seen hanging from lampposts and telephone poles, where “regular spiders wouldn’t be caught dead.”
The latest findings don’t definitively prove that the spiders’ relaxed behavior is the reason for “their affinity for urban environments,” the study says, adding that more research is needed. They do, however, reinforce Davis’s February research, which also found that Joro spiders aren’t necessarily bothered by the increased noise and vibration that come with city living.
“These Joro webs are everywhere in the fall, including right next to busy roads, and the spiders seem to be able to make a living there. For some reason, these spiders seem to be tolerant of urban environments,” Davis said of his previous research.
Alexa Schultz, a UGA graduate student and co-author of the study, agreed, saying, “It seems like Joro spiders will not hesitate to build a web under a red light or in an area where you wouldn’t expect a spider to be.”
But don’t worry: even though spiders are venomous, they pose no danger to humans, although they can raise your heart rate more than you raise theirs.
