Magnetic cells put biologists in a spin

Trout's nose might hold secret to homing sense

By Richard Chirgwin, 9th July 2012

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Scientists have long believed that some kind of magnetic sense lies behind some animals’ navigation ability, which in the case of some fish and birds seems to operate without the need for obvious landmarks. Now, a German researcher believes he has tagged individual cells that respond to magnetic fields.

Doing so needs a fair bit of patience, however: Stephan Eder of Munic’s Ludwig-Maximilians University first surrounded his collection of cells with a rotating magnetic field, and then watched to see which cells began to spin.

The rainbow trout was chosen because, back in 1997, a researcher called Michael Walker identified possible magnetoreceptors in its nose, spotting cells that contained iron crystals.

Eder confirmed this – but the crucial cells aren’t easy to spot. Placing the tissue samples in a slowly rotating magnetic field, he found that just one in 10,000 started spinning in time with the field.

According to this report over at Discover, the rarity of the cells isn’t a fluke: study leader Michael Winklhofer said “The cells are strongly magnetic, and if they are spaced too closely, they interfere with each other, which would deteriorate the sensitivity of the magnetic sense.”

The cells’ sensitivity to magnetic fields also turned out to be much stronger than expected, as is noted in the abstract of Eder’s paper, published in PNAS. ®

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