Earthworms use magnetism for their subterranean mapping
An earthworm has no eyes, which is fine, because even if they did they wouldn’t have much to look at. While they can sense vibrations, they don’t have ears to listen with. Instead, it seems that worms have a sort of subterranean GPS system in their heads, but instead of checking in with a satellite in space, they’re getting feedback from the North and South Poles.
A specialized sensory neuron has recently been identified that lets the worms detect magnetic fields. The small, antenna-shaped neuron is then used to help the worm have a point of reference and know if it’s crawling deeper into the earth, or heading towards the surface. This was even verified with worms from different hemispheres, who each displayed opposite reactions to magnetic stimuli thanks to their native points of magnetic reference.
As exciting as this internal compass is for the worms, researchers are most excited about having isolated the neuron making this all possible. A variety of other animals, such as some migratory birds, are known to be sensitive to magnetism, but this is the first time a specific neuron has been identified as the key to such an ability. It now provides a model that can be compared to more complicated species so we can better understand how they operate, and how to minimize our accidental interference with those signals.
Source: Worms Know What's Up — And Now Scientists Know Why by Bill Chappell, The Two-Way