When spinning webs in microgravity in the International Space Station (ISS) in orbit, spiders use light as a reference point, a study found.
In their natural habitat on the Earth’s surface, our eight-legged friends weave webs that are slightly asymmetrical – with their centers slightly closer to the top edge.
The spider sitting on this center can afford to travel further through the web to catch captured prey, as they can move faster in the direction of gravity.
However, it was unclear how spinning in a low-gravity environment would affect the web spinning process – which is why NASA sent spiders to the ISS to investigate.
While originally intended as a “simple” experiment to get the attention of American high school students, the results have turned out to be unexpected and far-reaching.
When spinning webs in the microgravity of the International Space Station (ISS) in Earth’s orbit, spiders use light as a reference point, a study found. Pictured, a spider on the ISS
In their initial study in 2008, NASA sent two intrepid ‘arachnauts’ to the ISS – one a labyrinth orbweaver (‘Metepeira labyrinthea’), as the main subject, and as a backup, another species of orbweaver, Larinioides patagiatus, in case the did not survive at first.
Unfortunately, the test did not go as planned. First, one of the spiders from his cage broke into his comrade’s – meaning the two spiders ended up spinning a tangled tangle of webs in their unexpectedly shared space.
In addition, the flies were brought in as a food source for the spiders that were bred at an unexpected rate, eventually covering the window in the experimental cage so that the arachnids were completely darkened after a month.
In a second attempt in 2011, Denver Museum of Nature & Science biologist Paula Cushing and colleagues instead sent two spiders of the same species – Trichonephila clavipes, the “ golden silk ball weaver ” – into separate cages.
Two other golden silk ball weavers were also monitored in earth cages to serve as a control for comparison. Each cage was equipped with three cameras. Sometimes the spiders were allowed to spin their webs under lamp light and sometimes in the dark.
The team recorded a total of 14,500 still images of the spiders as they spun their webs, dismantled and new spiders – from which they could study a total of 100 different web configurations.
The team found that webs spun in microgravity and in darkness were more symmetrical than those on Earth’s surface – with the center of each closer to the true center.
Plus, in these conditions, the spiders didn’t always position themselves on their webs with their heads down – ready to fall – like on Earth.
However, when they worked under lamp light, the researchers noted that the cobwebs became asymmetrical again – with the centers of the webs closer to the light and the arachnids turning themselves away from the lamp.
“We did not suspect that light would play a role in orienting the spiders in space,” said author and biologist Samuel Zschokke from the University of Basel.
“We were lucky that the lights were mounted at the top of the room and not on different sides,” he explains.
‘Otherwise we would not have been able to discover the effect of light on the symmetry of webs in weightlessness.’
In their initial study in 2008, NASA sent two intrepid ‘arachnauts’ to the ISS – one a labyrinth orbweaver (‘Metepeira labyrinthea’), as the main subject, and as a backup, another species of orbweaver, Larinioides patagiatus, in case the did not survive at first. Unfortunately, the test did not go as planned. First, one of the spiders from his cage broke into his mate’s – meaning the two spiders ended up spinning a tangled mess of webs, see photo
The team found that webs spinning in microgravity and in darkness became more symmetrical (as shown, with the lights back on) than those on Earth’s surface. Plus, in these conditions, the spiders didn’t always position themselves on their webs with their heads down – ready to fall – like on Earth.
When working under lamp light, the researchers noted that the spider webs became asymmetrical again, as shown – with the centers of the webs closer to the light and the arachnids pointing themselves away from the lamp.
“That spiders have such a backup system for orientation seems surprising, since they have never been exposed to a non-gravity environment in the course of their evolution,” added Dr. Zschokke.
On the other hand, he explained, since spiders are in constant motion while spinning the web, secondary orientation could have advantages.
The full findings of the study are published in the journal The Science of Nature.