Scientists Discover The Body Part Used To Sense The Earth's Magnetic Field

John Donges/Flickr. CC BY-NC-ND 2.0
Josh Davis 18 Jun 2015, 17:09

From salmon, to geese, to turtles—many animals move and migrate in relation to the Earth’s magnetic field. With no obvious sense organ to detect the magnetism, it’s long puzzled scientists as to how they manage this. But a group of researchers from the University of Texas think they may have found the answer.

After observing how a type of worm wriggles through soil, it was discovered that they possess a sensor on the end of a particular type of neuron, which allows them to align themselves in the correct orientation. Due to the similarities in brain structure across species, the researchers claim that it’s likely other animals share this sensor too.

Inside the head of the worm C. elegans, the TV antenna-like structure at the tip of the neuron (green) is the first identified sensor for Earth’s magnetic field. Andrés Vidal-Gadea/University of Texas

“Chances are that the same molecules will be used by cuter animals like butterflies and birds,” said Jon Pierce-Shimomura, who co-authored the paper published in the journal eLife. “This gives us a first foothold in understanding magnetosensation in other animals.”

The nematode worms, called Caenorhabditis elegans, are widely used for all sorts of biological studies, from aging to addiction. Whilst documenting the behavior of specimens from different parts of the world, the researchers noted that they didn’t all move down through the soil, as they normally do. They found that depending on where the worms were collected – either Hawaii, England, or Australia – the animals moved at the precise angle of the magnetic field that was equivalent to the down direction of their ‘home’ soil.     

The neuron suspected of housing the magnetic sensor was already known to be used to sense humidity and carbon dioxide levels. But when the researchers genetically modified the worms to have a break in the neuron, they found that the worms were not able to orientate themselves in the soil. In addition to this, they were able to show that changes in the magnetic field activated the neuron.

It was previously assumed that the worms migrated down by using gravity as a cue, but this finding suggests otherwise. “I'm fascinated by the prospect that magnetic detection could be widespread across soil dwelling organisms,” said Andrés Vidal-Gadea, the study’s lead author.

Previous research has found that certain brain cells in pigeons also handle information about magnetic fields to help them navigate, and others have suggested that certain cells in the noses of trout respond to magnetism, but this is the first time that researchers have managed to find a specific neuron that responds to the magnetic field. They think that this new knowledge could help protect crops from pests by manipulating the magnetic field in the area. 

[Header image: John Donges/Flickr]

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