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Birds Use Iron Balls In It's Brain To Sense Magnetic Field |
Where would people be without magnetic compasses? The short answer is: lost. By giving human beings a sixth sense—an ability to detect the hitherto invisible magnetic field of the Earth—the compass proved one of the most important inventions ever.
In the days before GPS, we needed both a compass and a map to navigate. Migrating birds are no different. Studies have suggested that the animals rely on an internal map and compass to traverse large distances, though just where these senses reside is unclear.
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Cells from the inner ear of pigeons stained with |
David Keay with his research team has found microscopic iron balls in the thinly sliced neurons of a pigeon's inner ear. For four years, Keays' team had been searching for the cellular receptor that allows birds to sense
magnetic fields. This ability allows some birds to migrate thousands of miles, but no scientist has definitively found the anatomical structure responsible.
In May of last year, however, a study published in the journal Science suggested that pigeons sense magnetic fields with neurons in their inner ears. So Keays, of the Research Institute of Molecular Pathology in Vienna, and his colleagues looked in this region, and all of the sudden, they struck iron. (Keays' team was looking for this metal since it's one of the few substances in the body that is magnetic.)
"As far as we know, they are the only iron-rich sensory neurons that have been described … and this is why it's such an exciting discovery," Keays told LiveScience.
These iron-containing membranes were found inside so-called "hair cells," which play a role in hearing and sensing movement and acceleration. So far, it's unclear exactly what they do, although Keays said the iron-imbued neurons are the most promising candidates for explaining birds' ability to sense Earth's magnetic field.
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The iron-containing membranes were found inside so-called "hair cells," which play a role in hearing and sensing movement and acceleration |
"I wouldn't say we've solved the puzzle," Keays said. "I would say we have another piece. However, if it does act as a magnetic receptor, it's probably in the right cells and right place." So far these iron-filled receptors appear to exist in every species of bird surveyed, he added.
David Dickman is a neuroscientist at the Baylor College of Medicine who co-authored the 2012 Science paper that found that cells in pigeons' inner ears sense magnetic fields. The fact that these iron "balls" are in the inner ear is fascinating, and it'll be exciting if they turn out to be involved in sensing magnetic fields, said Dickman, who wasn't in involved in this study, which was published online April 25 in the journal Current Biology.
The receptors could also possibly be used to enhance birds' ability to hear low-frequency sounds, or store iron for some as-yet-unknown purpose, Dickman said.
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