Spiders in space orient themselves by light

Shane McGlaun - Dec 11, 2020, 5:59am CST
Spiders in space orient themselves by light

One of the interesting things about space is that it’s hard to tell which way is up in micro or no gravity. Scientists have been sending spiders into space to see how the spider’s web-making ability changes in the microgravity aboard the ISS. As simple as it sounds on the surface to put a spider in space and see how microgravity affects web making, it was challenging to achieve.

The question NASA wanted to answer with the experiments was what an arachnid would do in zero gravity. On Earth, spiderwebs are asymmetrical, and the center is displaced towards the upper edge. When resting, spiders sit head down because it allows them to move towards freshly caught prey in the direction of gravity. The question was, what would spiders do in the absence of gravity.

In 2008, NASA sent a spider into space to inspire middle school students in the US with the experiment. The complexity of the task led to mishaps. Two different spider species were taken to the ISS, including a single Metepeira labyrinthea as the primary experiment and a Larinioides patagiatus as a reserve in case the first one didn’t survive.

The first mishap was that the backup spider managed to escape the storage chamber into the main chamber and couldn’t be recaptured due to safety reasons. That meant an additional spider and the two spun webs that got in each other’s way. Another challenge was that the flies sent to be food for the spiders reproduced more quickly than expected, meaning the larvae crawled out of the breeding container on the floor of the case to the experiment chamber.

The fly larvae reproduced so quickly that the spiders couldn’t be seen behind all the fly larvae after a month. What was discovered about how spiders orient themselves in zero gravity was a surprise. Scientists say they wouldn’t have guessed light would’ve played a role in orienting the spiders in space. The lamps inside the cases were attached to the top of the chamber and not on various sides, a coincidence that allowed scientists to discover that light impacts the symmetry of webs in zero gravity.

Analyzing pictures of the spider experiments showed that when the lights were turned off, the spiders oriented themselves in arbitrary directions. When the lights were on, the spiders use them as an orientation aid. Spiders can build webs in the dark and don’t need light to hunt, making the finding of light assisting with orientation a surprise.

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