Caenorhabditis elegans transfers across a gap under an electric field as dispersal behavior

Abstract

Interactions between different animal species are a critical determinant of each species' evolution and range expansion. Chemical, visual, and mechanical interactions have been abundantly reported, but the importance of electric interactions is not well understood. Here, we report the discovery that the nematode Caenorhabditis elegans transfers across electric fields to achieve phoretic attachment to insects. First, we found that dauer larvae of C.elegans nictating on a substrate in a Petri dish moved directly to the lid through the air due to the electrostatic force from the lid. To more systematically investigate the transfer behavior, we constructed an assay system with well-controlled electric fields: the worms flew up regardless of whether a positive or negative electric field was applied, suggesting that an induced charge within the worm is related to this transfer. The mean take-off speed is 0.86m/s, and the worm flies up under an electric field exceeding 200kV/m. This worm transfer occurs even when the worms form a nictation column composed of up to 100 worms; we term this behavior "multiworm transfer." 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, 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.