Who Knew? Light Is the Key to Spiders Weaving Webs in Space

Spider building an asymmetric web in weightlessnessBioServe Space Technologies, University of Colorado at Boulder

I’m willing to bet a lot of people (myself included) are terrified of spiders. But that doesn’t mean they aren’t interesting. In one two month study Led by Paula Cushing of the Denver Museum of Nature and Science and Samuel Zschokke of the University of Basel on the International Space Station, the scientists discovered that the spiders Trichonephila clavipes use lights as a substitute for gravity when placed in the outer space not only orient and position themselves but weave their webs.

The duo used three cameras set to take a photo every 5 minutes. They had two spiders on Earth and two “arachnauts” in space. Each was locked in its own case, in a controlled habitat. In total, they took 14,528 photos. Scientists were able to use 14,021 because it showed the spiders in a resting position.

Normally, they build their webs asymmetrically, with their hubs near the top. The hub is a place where a spider hangs out while waiting for its prey to stumble on the web. They usually face down, in the direction of gravity, until the prey arrives.

But Cushing and Zschokke found that in zero gravity, a source of light was a key factor in how spiders wove their webs. When present, the spiders built their webs the same way they would on Earth (asymmetrically) with their hubs on top.

Where things got interesting was when scientists turned off the lights. In this environment, spiders systematically wove symmetrical webs without any orientation preference, and their hubs were usually closer to the center. On Earth, spiders tend to turn downward while waiting for prey. In space, things turned out differently. Without light, the spiders were much less likely to face the downside. But by leaving the lights on when the spiders were weaving webs, they were directing them downward in a more consistent fashion. The spiders also did not respond to the change in lighting for an hour, maintaining the orientation they had chosen.

This led Zschokke and Cushing to conclude that spiders use light as a surrogate to decide their orientation when there is no gravity. The eight-legged creatures also used light to get closer to the top of the web. The researchers had not even considered the light when starting the experiment.

Spider building a symmetrical web in zero gravityBioServe Space Technologies, University of Colorado at Boulder

Zschokke said: “We wouldn’t have guessed that light would play a role in orienting spiders in space.” He said: “We were very lucky that the lamps were attached to the top of the chamber and not from multiple sides. Otherwise, we would not have been able to discover the effect of light on the symmetry of the canvases in weightlessness.

It’s amazing that spiders were able to adapt to the lack of gravity. Even Zschokke was shocked, saying, “That spiders have a back-up system for orientation like this seems surprising, as they have never been exposed to a non-gravity environment during their evolution.

But not everything went as planned. For example, they planned to have four female spiders for the experiment. They were chosen as juveniles and it turned out that they discovered that two of them were males. Scientists wanted to control sex, because the structure and size of a spider’s body is different, depending on its sex once they have reached full growth. The good news is that only one of the males made it to the ISS, while the other remained on Earth.

Putting anything in outer space is always interesting. The fact that the spiders were able to instantly adapt to the lack of gravity is absolutely breathtaking. It makes me curious about how other animals can react in the great unknown.

Source: University of Basel via Gizmodo

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