Researchers working with bumblebees have discovered that they can detect the electrical signals of flowers thanks to the vibrations of their tiny hairs. The findings are published in Proceedings of the National Academy of Sciences this week.
Electroreception is common in aquatic animals – from fish to rays to dolphins – who use saltwater as a conductive medium. In fact, the phenomenon was first discovered in sharks: They have sensitive, jelly-filled receptors for detecting fluctuations in electric fields as they hunt prey in seawater. On land, echidnas use electrosensory organs in their snout to detect prey hiding in wet soil. Recent work revealed that flowers communicate with their pollinators by sending out electrical signals. But dry air is a nonconductive medium, which means these electric fields are weak. Exactly how bees detect and interpret them has remained a mystery.
To investigate, a University of Bristol team, led by Gregory Sutton, used a non-contact laser to measure tiny vibrations in the antennae and the tiny hairs of Bombus terrestris bumblebees. They found that both antennae and hairs move in response to electric fields – but the hairs move more rapidly, and they were also displaced more. When the team focused on neuron activity, they found that hair deflections in response to an electric field elicited a nervous system response. That means that hair, and not the antenna, alert the bee's nervous system to floral signals.
"We were excited to discover that bees' tiny hairs dance in response to electric fields, like when humans hold a balloon to their hair," Sutton said in a statement. You can watch a video of bee hair moving in response to an electrical field here.
Electroreception in bumblebees likely arose because of the low mass and high stiffness of their so-called mechanosensory hairs. The rigid, lever-like motion within a socket resembles spider hairs and mosquito antennae that are acoustically sensitive. Furthermore, mechanosensory hairs are common in arthropods, a group that includes insects and spiders. It’s possible that electroreception in terrestrial animals is more widespread than we previously thought.