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鈥檚 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鈥� 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鈥檚 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鈥檛 start their jump close to the fly never successfully hit their target.
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To further investigate whether worms鈥� 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鈥� motion, the team learned which way electromagnetic forces push or pull charged objects at any point near the fly. Then, Jim茅nez and his colleagues overlaid the worms鈥� trajectories onto this map, and found the worms鈥� 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 Jim茅nez. Additionally, the worms typically 鈥渟tand up鈥� their bodies before they jump, which makes their tails grounded and their heads slightly charged in comparison.
鈥淲e don鈥檛 know yet if the worms can sense electricity, but if electrostatic forces help them jump at all, that could be an evolutionary advantage. It鈥檚 hard to jump onto a moving insect, and whenever a worm misses, it doesn鈥檛 get to eat,鈥� he says.
Jim茅nez presented the work at a meeting of the in Las Vegas, Nevada, on 6 March.
