Scientists have discovered the first sensor of the Earth's magnetic field in animal, which could solve the mystery of how the internal compasses that help animals migrate work.
The elusive sensor was spotted in the brain of a tiny worm C. elegans, the University of Texas at Austin reported. It is a microscopic structure at the end of a neuron that is believed to be present in other animals.
"Chances are that the same molecules will be used by cuter animals like butterflies and birds," said Jon Pierce-Shimomura, assistant professor of neuroscience in the College of Natural Sciences and member of the research team. "This gives us a first foothold in understanding magnetosensation in other animals."
The team observed hungry worms in gelatin-filled tubes tend to move downwards in what the researchers thought was in search of food, but when worms from other parts of the world were brought in they didn't all move in the same direction. Worms from regions such as Hawaii, England, and Australia, were observed to move a precise angle that corresponded with what would have been "down" if they had been at home. For example, the Australian worms moved upwards in the tubes, which corresponds which would be "downwards" according to that region's magnetic field. The finding is significant because species that live in the soil tend to migrate downwards.
The neuron that contains the magnetic field sensor is called an AFD neuron, which has already been found to sense carbon dioxide levels and temperature. The researchers tested the worms' magnetosensory abilities by altering the magnetic field around them with a magnetic coil system and observing how they reacted. They also found worms that were genetically engineered to have a broken AFD neuron were not able to orient themselves with the magnetic field. Finally, these used a technique called calcium imaging to reveal changes in the magnetic field caused the AFD neuron to activate.
"It's been a competitive race to find the first magnetosensory neuron," Pierce-Shimomura said. "And we think we've won with worms, which is a big surprise because no one suspected that worms could sense the Earth's magnetic field."
The findings were published in a recent edition of the journal eLife
