Spiders in space: without gravity, light becomes key to orientation

by | Dec 11, 2020 | Daily Space, Science, Space History | 0 comments

Spiders in space: without gravity, light becomes key to orientation
IMAGE: A specimen of the spider species Trichonephila clavipes on board the international space station ISS. CREDIT: BioServe Space Technologies, University of Colorado Boulder

As some of you may remember, back during the shuttle program, some students had a cool project to study how spiders form webs in zero-g selected to fly. This particular experiment did not go well and was, in fact, the kind of spectacular failure where things go so wrong you have to laugh. I’m going to simply quote from a summary from the University of Basel.

Two specimens from different spider species flew to the International Space Station (ISS) as “arachnauts,” one (Metepeira labyrinthea) as the lead and the other (Larinioides patagiatus) as a reserve in case the first didn’t survive.

The reserve spider managed to break out of its storage chamber and into the main chamber. The chamber couldn’t be opened for safety reasons, so the extra spider could not be recaptured. The two spiders spun somewhat muddled webs, getting in each other’s way.

And if that were not enough, the flies included as food reproduced more quickly than expected. Over time, their larvae crawled out of the breeding container on the floor of the case into the experimental chamber, and after two weeks covered large parts of the front window. After a month, the spiders could no longer be seen behind all the fly larvae.

Needless to say, there wasn’t a lot learned from this experiment, beyond flies thrive in zero-g and spiders are always escape artists.

This failed experiment left researcher Paula Cushing wondering what could have been, and in 2011, she was able to work with Dr. Samuel Zschokke to do a better experiment. Their results are now published in the journal The Science of Nature.

Their intention was to launch two identical spiders in identical habitats into space, and have two control spiders on Earth. While they meant to have four female spiders, it turned out that two of their spiders were actually male-presenting once they grew large enough to be easily differentiated, but one of those boys was on the Earth and the other was in space, so the research could proceed.

Here on Earth, spiders are known to build their webs in all kinds of lighting and lack of lighting conditions. In general, those webs have the highest density area – that bulls-eye of concentric rings we call the center – actually off-center and located higher up in the web. The spiders typically hang out on that nexus with their head facing downward as they wait for prey to get stuck.

Because spiders build identical webs with and without light, it was assumed light played no role in web construction.

But, you know what they say about assumptions…

In the 2011 spiders-in-space experiment, researchers studied webs the spiders spun both with and without light, and watched how the spiders oriented themselves. Webs woven in darkness turned out to be symmetric, while those built while the habitat was illuminated from the top had the same asymmetric shape as those seen on Earth. Without light, the spiders randomly oriented themselves, but with that light turned on, they hung head down.

It turns out, in the absence of weight, spiders will look to the light for orientation. It’s cool that even arachnids have backup systems for when the pull of the Earth seems to go away.

I would like more of this science, please.

More Information

University of Basel press release 

Spiders in space—orb-web-related behaviour in zero gravity,” Samuel Zschokke, Stefanie Countryman & Paula E. Cushing, 2020 December 3, The Science of Nature

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