Tiny parasitic worms may be exceptionally good at jumping onto their prey because they are electrically attracted to them.
Roundworms (Steinernema carpocapsae) that attach to insects like bees or fruit flies to feed on them are among nature’s most powerful jumpers despite being only a millimetre long. They launch into the air, then spin in a series of flips until they land on insects headfirst. Researchers have previously studied how the structure of the worms’ muscles helps them jump so well, but at the University of Maine and his colleagues now think that that electric attraction between them and their prey might play a role as well.
The researchers used a high-speed camera to record worms jumping onto a fruit fly that was held in place a few millimetres above it. When the team applied a small electric voltage to the insect, the worm’s trajectory would a sharp, mid-air turn towards the fly, no matter where it started its jump. In experiments where the researchers made the fly electrically neutral, worms that didn’t start their jump close to the fly never successfully hit their target.
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To further investigate whether worms’ jumping paths changed because of electric attraction to the fly, the researchers made a map of the electric field around the fly by putting the charged insect in air filled with charged, dust-like particles. By recording the particles’ motion, the team learned which way electromagnetic forces push or pull charged objects at any point near the fly. Then, Jiménez and his colleagues overlaid the worms’ trajectories onto this map, and found the worms’ aerial paths aligned with those of the charged particles close to the fly, suggesting jumping worms are pulled towards the insect by electric attraction.
In nature, flying insects build a static electric charge as they flap their wings against particles of air, so the experiment imitated natural conditions by charging the fly, says Jiménez. Additionally, the worms typically “stand up” their bodies before they jump, which makes their tails grounded and their heads slightly charged in comparison.
“We don’t know yet if the worms can sense electricity, but if electrostatic forces help them jump at all, that could be an evolutionary advantage. It’s hard to jump onto a moving insect, and whenever a worm misses, it doesn’t get to eat,” he says.
Jiménez presented the work at a meeting of the in Las Vegas, Nevada, on 6 March.
