Tiny Worms Discovered an Ingenious Way of Riding on Bumblebees

Tiny worms have found a way to travel by hitchhiking on other animals, and scientists have now discovered that they use electricity to "jump" on their ride.

According to a paper published in the journal Current Biology on June 21, microscopic Caenorhabditis elegans worms can leap through the air and attach themselves to insects like bumblebees by using electrical fields.

The worms were found to leap at a high speed, and "simply stick to their ride due to it being charged," study co-author and biophysics professor at Hiroshima University in Japan, Takuma Sugi, told Newsweek.

The authors explained in the paper that the worms would even pile together and jump in a large group towards a bumblebee, hitching a ride all at once.

"The mean take-off speed is 0.86 m/s (meters per second), and the worm flies up under an electric field exceeding 200 kV/m (kilovolt per meter). This worm transfer occurs even when the worms form a nictation column composed of up to 100 worms; we term this behavior 'multiworm transfer,'" the authors wrote.

Bumblebees have a natural charge, like most animals, but this charge can be increased after they rub themselves onto pollen—similar to rubbing a balloon to increase its static charge.

"​​These observations led us to conclude that C. elegans can transfer and attach to the bumblebee Bombus terrestris, which was charged by rubbing with flower pollen in the lab. The charge on the bumblebee was measured with a coulomb-meter to be 806 pC (picocoulombs), which was within the range of bumblebee charges and of the same order of flying insect charges observed in nature, suggesting that electrical interactions occur among different species," the paper says.

This implies that C. elegans may also like to ride other pollinators.

Being able to stick to passing insects may be beneficial to the worms as it allows them to disperse much further than they can on their own.

"There is a possibility that dispersal and the resulting distributions of very small animals have significant effects on both ecology and evolution because these submillimeter animals are at the bottom of the food chain," Sugi said.

"For small animals, especially wingless and legless animals such as worms, dispersal and host-seeking are crucial problems because their migration processes are very slow and energetically costly," Sugi continued.

"Therefore, as a dispersal strategy, smaller animals are attached to passing larger animals, such as insects or birds, to move over long distances. This kind of interaction, in which an animal uses a host animal for the purpose of dispersal, is called phoresy. Nematodes are typical examples of these small animals."

Other animals have been seen to use electrostatic fields to their advantage in small ways. Fish species such as electric eels can sense predators and prey nearby using an electric sensing organ, while bumblebees themselves are capable of detecting the electric fields found around flowers.

The exact mechanisms behind how these tiny worms lock onto the charge of their rides are unclear, or if this behavior is possible in other closely related species of worm. Similar leaping behavior has been spotted in related species—Caenorhabditis briggsae and Caenorhabditis japonica—suggesting that other species may also be capable of this feat, although more research needs to be done to find out if they work the same way.

"Because C. elegans is a model organism, unlike other submillimeter animals, genetic methods have been well established to study the relationship between behavior, neural activity, and genes," the authors wrote in the paper. "Therefore, further studies on the electric field and the behavior of C. elegans are expected to provide more details on the electrical ethology of microorganisms."

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