“Boarding” by electric jump

Video: A nematode jumps onto the hairy body of an electrostatically charged bumblebee. © Current Biology/Chiba et al.

Worms can only crawl, you might think. But now a study shows that at least small nematodes are also capable of jumping: These research model animals apparently use electrostatic forces of attraction in a targeted manner to whiz through the air from A to B. For example, they can land on bumblebees and then be transported through the air by them. The researchers say it is possible that this electrical method of boarding is also common among other tiny creatures.

It is the worm of science: The nematode Caenorhabditis elegans is used worldwide as a model organism in laboratories, especially in developmental biology and genetics. These roundworms, which are up to about one millimeter long, naturally live in the soil and feed on bacteria there. However, C. elegans can also be cultivated comparatively easily in culture vessels for research purposes. Due to the intensive research on this little animal, a lot is already known about its characteristics and behavior. But now a Japanese research team has revealed another, literally exciting ability of the tiny creatures.

How do the worms get to the lid?

As the scientists report, the discovery started with an observation during the usual work with the test animals in the laboratory: they noticed that the worms they had bred were surprisingly often found on the lids of the Petri dishes that are opposite the culture medium. So the researchers wondered how they get there. To clarify this, they targeted the tiny creatures with video cameras. By recording, the scientists then discovered that the worms weren’t just crawling up the walls of the dish: they observed some nematodes jumping from the bottom of the dish to the ceiling.

The researchers then conducted experiments to get to the bottom of this phenomenon in more detail. It quickly became clear that the jumps are based on an electrostatic force: compared to the base, the lid of the Petri dish can have an electrical charge that is sufficient to ensure an attractive force with a jumping effect. This is the effect that makes hair stand on end, for example, when a balloon charged by friction approaches.

Through experiments with charged glass electrodes, the researchers were finally able to show more precisely how the worms react to differences in potential. It became apparent that this is not just a passive effect: the worms apparently straighten up when they sense an electrostatic force in order to be carried away by it. “The worms stand on their tails to reduce the surface energy between their bodies and the substrate, making it easier to attach themselves to objects,” says co-author Takuma Sugi of Hiroshima University.

Hop-on method for air travel

But why should they do that? As the team explains, the behavior could serve to spread the worms “by hitchhiker”: It is known that C. elegans attaches itself to snails in order to allow them to move around in an energy-saving manner. However, the worms have also been found on winged insects. In contrast to snails, it was unclear how the tiny creatures climbed onto these means of transport. The current discovery now offers a possible explanation for this. “It is known that pollinators like insects and hummingbirds are electrically charged,” says Sugi.

In order to find out to what extent the worms can actually use this potential to jump up, he and his colleagues carried out experiments with bumblebees. To do this, they gave the insects electrostatic charges, which can also occur naturally, and used them for experiments with C. elegans. It turned out that when the worms got close to the bumblebees and felt the charge, they stood on their tails and finally jumped on board over a maximum distance of 2.4 millimeters. Some worms even piled on top of each other and then jumped onto the bumblebees together in columns. The researchers conclude that it thus became clear that the phenomenon can have ecological significance for nematodes and possibly also for other small organisms.

Video: A cohesive group of worms take off together. © Current Biology/Chiba et al

Through further investigations, they now want to devote themselves to the question of what the “talent” of C. elegans for electro-jumping is based on. According to them, it is advantageous that this is a model organism: “There are well-established genetic methods for investigating the relationship between behavior, neuronal activity and genes,” the scientists write. According to the team, it may therefore be possible to uncover certain predispositions that play a role in electrostatic jumping behavior.

Source: Cell Press, Article: Current Biology, doi: 10.1016/j.cub.2023.05.042

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