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Navigating by the Earth’s Magnetic Field

Migrating geese, sea turtles, wolves—and worms—find their way.  And for the first time scientists think they know how.

c_elegans

c_elegans
Photo from www.genome.gov

A team of scientists and engineers at the University of Texas at Austin has identified the first sensor of the Earth’s magnetic field in an animal, in the brain of a tiny worm. The sensor, found in worms called C. elegans, is a microscopic structure at the end of a neuron, and looks like a nano-scale TV antenna. The worms use it to figure out which way is down, as they scavenge for food.

This AFD neuron was already known to sense carbon dioxide levels, humidity, and temperature, all very handy things to know if you’re a worm.

The discovery came about as the researchers noted that C. elegans in gelatin-filled tubes moved in the direction that the worms believed was down. When they tested this phenomenon in their lab with C. elegans from various places on the globe, they observed that all of the worms didn’t move down—in fact, Australian worms moved up. Each of the worms moved at a precise angle to the magnetic field that would have corresponded to down if they had been in their local environments. Each worm’s magnetic field sensor system is apparently finely tuned to where it lives.

When the researchers altered the magnetic field around the worms, they noted that the worms changed direction to their new “down.” Worms that were genetically engineered without the AFD neuron weren’t able to orient themselves up or down.

The researchers believe that other animals probably have similar sensors, given similarities in brain structure across species. (One of the scientists has suggested that it might be possible to manage agricultural pests by manipulating magnetic fields. I find myself wondering what the unintended consequences of that will be.)

The research was published in the journal eLife in June.

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