Eder, Stephan H. K.; Cadiou, Herve; Muhamad, Airina; McNaughton, Peter A.; Kirschvink, Joseph L.; Winklhofer, Michael
Magnetic characterization of isolated candidate vertebrate magnetoreceptor cells.
In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 109, No. 30: pp. 12022-12027
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Over the past 50 y, behavioral experiments have produced a large body ofevidence for the existence of a magnetic sense in a wide range ofanimals. However, the underlying sensory physiology remains poorlyunderstood due to the elusiveness of the magnetosensory structures. Herewe present an effective method for isolating and characterizingpotential magnetite-based magnetoreceptor cells. In essence, a rotatingmagnetic field is employed to visually identify, within a dissociatedtissue preparation, cells that contain magnetic material by theirrotational behavior. As a tissue of choice, we selected trout olfactoryepithelium that has been previously suggested to host candidatemagnetoreceptor cells. We were able to reproducibly detect magneticcells and to determine their magnetic dipole moment. The obtained values(4 to 100 fAm(2)) greatly exceed previous estimates (0.5 fAm(2)). Themagnetism of the cells is due to a mu m-sized intracellular structure ofiron-rich crystals, most likely single-domain magnetite. In confocalreflectance imaging, these produce bright reflective spots close to thecell membrane. The magnetic inclusions are found to be firmly coupled tothe cell membrane, enabling a direct transduction of mechanical stressproduced by magnetic torque acting on the cellular dipole in situ. Ourresults show that the magnetically identified cells clearly meet thephysical requirements for a magnetoreceptor capable of rapidly detectingsmall changes in the external magnetic field. This would also explaininterference of ac power-line magnetic fields with magnetoreception, asreported in cattle.