Weightless Flies Have Wanderlust

To astronauts, science fiction writers, and entrepreneurs selling tickets on private space flights, the question of how weightlessness affects an organism is crucial. Our cells and organs are fine-tuned for life within the comfortable harness of Earth's gravity, so what happens to them when we're cut loose? There's at least one way to study this question without the prohibitive price tag of sending something all the way to space. A group of magnetically levitated fruit flies, though they couldn't report on their experience, seemed to find it just as good as the real thing.

University of Nottingham researcher Richard Hill and his colleagues used a powerful magnetic field to create a small, zero-gravity "arena" for fruit flies. Though magnetic fields attract magnetic substances such as iron, they also weakly repel certain other materials that are called "diamagnetic." These include water and organic matter--in other words, most of what's in a fruit fly. (Or in you. But there isn't a magnet big enough to try this trick on a person.)

By carefully aligning their disc-shaped fly arenas inside a superconducting solenoid magnet, the researchers were able to create environments of roughly 1g (equal to Earth's gravity), 2g (twice Earth's gravity), and 0g (whee!). They also left one fly dish outside the magnet, so they could compare the 1g environments and make sure the magnetic field didn't just make all the flies crazy.

Though the researchers provide many mathematical descriptions of their result, you can see it easily and immediately in this video. The 0g flies are on the top left.

Fruit flies' normal behavior is to roam, but the 0g flies are tearing around their dish.

Unlike human astronauts, who don't have much choice but to float, fruit flies have grippy little feet and the power of flight. So the weightless flies spent most of their time walking on the floor, walls, and ceiling as usual. (You might spot a few of them floating dazedly in the center of the dish, though.) What was unusual was the speed and amount that they traveled.

This might be simply because it's easier for flies walk without gravity. If it takes less energy than usual to walk, a fruit fly that's putting the normal amount of effort into moving around will find itself at a near-sprint. The 2g flies supported this theory by walking more sluggishly than usual.

Another possibility is that the flies' altered perception of gravity affected their behavior. Like human astronauts who go ricocheting off the walls for fun, the fruit flies might have noticed something was different and reacted to that feeling.

The finding that weightless flies speed-walk isn't new: Experiments done on the International Space Station and on the space shuttle Columbia found the same result. But replicating the finding here on Earth shows that it wasn't a fluke caused by some other factor, such as the trauma of takeoff. The flies' altered behavior was directly due to their low-gravity environment, making it relevant to humans and any other organisms we might carry into space.

Hill's study also shows that zero-gravity experiments, at least on very small organisms, don't have to be done in space. Studies done inexpensively here on Earth can provide real insights into life in outer space, and help create safer technologies for the lucky humans who get to go.

Hill, R., Larkin, O., Dijkstra, C., Manzano, A., de Juan, E., Davey, M., Anthony, P., Eaves, L., Medina, F., Marco, R., & Herranz, R. (2012). Effect of magnetically simulated zero-gravity and enhanced gravity on the walk of the common fruitfly Journal of The Royal Society Interface DOI: 10.1098/rsif.2011.0715 


Movie: Hill et al., data supplement; Photo: NASA