Nematodes Jump Bumblebees Through Electric Fields – Ars Technica

nematode (C. elegans) jumps on a bee along a riding electric field. Credit: Chiba et al., 2023

Japanese scientists working with nematodes (C. elegans) One day, several lab-grown worms mysteriously remained attached to the lids of petri dishes instead of the dog food agar where they were originally placed. Intrigued, they conducted experiments to see how the worms moved from one point to another in less than a second.

The researchers found that, instead of crawling up the walls of the dish, the worms were jumping from the bottom of the dish onto the lid — and they were using electric fields to do so. They can even jump from a petri dish onto a bee, either individually or in large groups. The team described their work in new leaf Published in Current Biology.

“Pollinators, such as insects and hummingbirds, are known to be electrically charged, and pollen grains are thought to be attracted to the electric field formed by the pollinator and the plant,” said co-author Takuma Souji, a biophysicist at Hiroshima University in Japan. “However, it was not entirely clear whether electric fields are used for interactions between different terrestrial animals.”

The authors write that interactions between different organisms “strongly shape the structure and function of ecological communities and ecosystems.” Different species can depend on different environmental triggers: chemical reactions between insects and plants, for example; visual perception to spot prey and select preferred foods; and the ability to detect mechanical energy from other animals. Then there are electrostatic interactions. In addition to pollinators, the authors note that many species of fish use electric fields to sense prey and predators. and overgrown spiders – immortalized in E.B. White’s children’s classic Charlotte’s Network– Release the silk threads to form a parachute and float in the air.

How do spiders do this? One hypothesis is that spider webs have a static electric charge that interacts with the weak vertical electric field in the atmosphere. A competing hypothesis is that as the air warms as the sun rises, silk threads are emitted by the spiders to rotate their “umbrellas” to catch the convection updrafts (updraft) caused by temperature gradients. a Study 2018 found that spiders seem to be able to detect electric fields under normal atmospheric conditions. This leads to the ballooning behaviour, and the electric fields provide enough force to generate lift. last year, Physicists showed From a 3D numerical simulation, at least for small spiders, the electric fields are already sufficient to generate sufficient lift without the aid of air currents.

One of the reasons interactions between species have such a strong effect on ecosystems is that they aid in the dispersal of animals, which Charles Darwin considered crucial to the evolution and expansion of species. When one species depends on another for such dispersal, it is known as a dispersal humans. Small animals without wings and legs, such as worms, often attach themselves to larger, passing animals such as insects and birds to traverse great distances.

C. elegans It is found on a wide range of species and depends on a type of phoresy to achieve this range. Previous research suggested that in some cases, such as snails and some insects, the dispersal mechanism is rather simple. Nematodes engage in a behavior known as “percussion,” in which the worms stand on their tails, lowering the surface tension of the water in which nematodes are often found, making it easier for the worms to attach themselves to their dispersed hosts. per suji et al. This also increases the frequency of direct contact with other animals.

However, unlike snails and insects, flying insects such as bees naturally accumulate charge in flight, producing an electric field. Sujei and his colleagues thought that electrostatic interactions might explain why nematodes grown in the lab keep ending up on the lid of a petri dish. The first experiments confirmed that the worms were not crawling up the walls of the Petri dish. Switching to high-speed video enabled the team to capture the jumping motion on camera and ensure the worms leaned in before making the jumps. Nor did the worms appear to generate the jumping force, which indicates an external force at work.

To see if that external force is the electric fields, Suji et al. He did another experiment. They embedded a square array of micro-struts on the surface of the agar, mimicking the natural soil environment. They placed about 1,500 worms on an agar substrate and then placed them on top of a glass electrode. They placed a second glass electrode parallel to the first but separated by a small distance. Then they applied effort to find out what happened. The worms moved to the other electrode only when the charge was applied and moved at an average speed of 0.86 meters per second. This is close to the speed of human walking, and their speed increased as the electric field intensified.

Finally, the team rubbed pollen on the bees to create a natural electrical charge and placed the bees near the worms. When the bees were close enough, the worms stood up on their tails and jumped up to the bees. This worked even with groups of worms piled on top of each other, with one poor worm overloaded during transport.

The mechanism may now be clear, but Suji et al. I’m still not sure exactly how all this works. Luckily, C. elegans It is a typical organism and the relationship between its genes, behavior and neural activity has been studied extensively. Therefore, further studies on the electric field and its behavior C. elegans It is expected to provide more details about the electrical mythology of microorganisms.”

DOI: Current Biology, 2023. 10.1016/j.cub.2023.05.042 (about DOIs).

Listing image by Current Biology / Chiba et al.