Thursday, 12 July 2012

Magnetic Cells Give Sense of Direction to Fish

After spending 3 years at sea and traveling up to 300 kilometers away from home, a rainbow trout can swim straight back to its original hatching ground, following freshwater streams inland and rarely heading in the wrong direction. This remarkable feat of navigation likely relies on many senses; the fish have superb eyesight and smell. But the trout also seem to rely on Earth’s magnetic fields, which point them in the right direction. Now, for the first time in any animal, scientists have isolated magnetic cells in the fish that respond to these fields. The advance may help researchers get to the root of magnetic sensing in a variety of creatures, including birds.
“We think this will really be a game changer,” says Michael Winklhofer, an earth scientist at Ludwig Maximilians University Munich in Germany who led the new study. “To study magnetic sensory cells, you have to be able to get hold of them first, and that’s what we’ve finally developed a way to do.”

Previous research has shown that many species of fish, as well as migratory birds, have the ability to detect differences in magnetic field strengths, which vary around the globe. Scientists think that the key to this ability is magnetite, the most magnetic of all minerals, which they’ve found embedded in bird and fish tissues. They’ve even narrowed down which tissues in these animals could contain magnetite by using dyes that bind to the mineral. But they’ve never been able to isolate individual cells that contain magnetite, and some of the staining methods have led to false positives and controversy in the field.
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