Tiny nematode worms use static electricity to leap into the air, which may help them attach onto flying passers-by, such as bumblebees, and hitch a ride.
Caenorhabditis elegans worms measure around 1 millimetre long and are typically found living in soil and rotting plant material. The worms are known to travel on the bodies of winged insects, but how such minuscule creatures leap into the air has been a mystery.
Takuma Sugi at Hiroshima University in Japan and his colleagues may have finally figured this out. They first noticed that the worms they cultivated in the laboratory often ended up on the lids of Petri dishes. When the researchers filmed them to find out how they ended up in that position, they found that the worms seemed to jump from the dish to the lid in 0.1 seconds.
When some nematode species jump, they tend to bend their body and change their posture before take-off, but C. elegans worms stand on their tails and hardly move before leaping, which suggests their jumps are a result of external forces.
To test whether an electric field is responsible, the team placed 1500 worms on a glass electrode and set another glass electrode a few millimetres above it. When no voltage was applied, none of the worms leaped. When an electric field of 200 kilovolts per metre was applied, the worms jumped with an average speed of 0.86 metres per second, which increased with a stronger electric field.
The next step was to see if this electrically induced leaping behaviour could occur in nature. The researchers selected the bumblebee, an insect known to organically accumulate electric charge, as their subject.
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They charged anaesthetised bumblebees by rubbing them against a plant that is commonly found in their natural environment and placed them close to the worms. The worms stood on the ends of their tails to get closer to the bee, then leapt over a distance of 1.26 millimetres onto it.
Earlier this year, Víctor Ortega Jiménez at the University of Maine and his colleagues reported that a different nematode worm, Steinernema carpocapsae, uses static electricity to jump onto insects it parasitises.
Sugi’s results suggest that C. elegans, which isn’t a parasite, may also use electric fields to jump and attach onto insects in nature. This might allow it to migrate to new areas that have better resources in order to improve their chances of survival.
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“This discovery is really exciting because it is the first evidence that static electricity could be involved in animal phoresy, which is when one animal essentially hitchhikes a ride on another to get to a new or better location without significantly hindering the carrying animal, which is distinct from parasitism,” says Sam England at the University of Bristol, UK.
Future studies might look at the biological drivers behind the behaviour, how the worms’ genetics enables it and how they sense the electric field, says Sugi.
Journal reference:
Current Biology DOI: 10.1016/j.cub.2023.05.042
