Michael Winklhofer, a biogeophysicist at the University of Munich and colleagures have identified cells in the nose of trout that respond to magnetism. The researchers chose to study the olfactory tissues of trout based on decade-old research, which showed that magnetic fields affected the electrical activity of nerves that carried information from the fishes' noses. Instead of grinding up the tissues for analysis, as older methods tended to do, the researchers gently isolated whole cells from the tissues and put them into Petri dishes.
When the team applied rotating magnetic fields to those dishes, about one out of every 10,000 cells spun with the same frequency as the fields. luminated by the light of the microscope, structures inside of these cells also shone brilliantly, making them easy to detect. A closer look revealed crystals attached to inside the cell membranes that contained what appeared to be magnetite, an iron-rich magnetic material. Scientists don't yet know how these structures work, but Winklhofer suspects that they excite membranes inside neurons and trigger nerve impulses that send direction-related information to the brain.
Based on the abundance of magnetic cells in the samples, Winklhofer estimates that each fish had a total of between 10 and 100 of these cells in its nose. As expected, there were no magnetic cells in the animals' muscle tissue. Even more magnetic cells were detectable in the trout's lateral line, a sensory organ in fish that detects vibrations.