Although it has been strongly suggested that magnetism is the source for guidance in migratory animals, a new study seems to put the question to rest. The cells of certain migratory animals contain iron-rich crystals called Magnetite that are highly susceptible to earth's magnetic field.



Migration explained? Likely source of animals' magnetic sense identified

Researchers have isolated what are essentially tiny compass needles in the noses of rainbow trout that may explain these and many other animals' incredible ability to navigate across vast distances.

When cells scraped from the trout's nasal passages were placed in a rotating magnetic field, a clump of tiny iron-rich crystals inside the cells called magnetite — the same mineral used in compass needles — spun in synchrony with the field, turning the cells around with them.

The strength of the crystals' magnetic response, and their firm attachment to the surrounding cell membranes, lent strong support for what scientists have long suspected: That these crystals lean back and forth like a sail in response to Earth's weak magnetic field, and that the cells they are embedded in somehow convey their swaying movements to the brain. This is believed to confer trout and other migratory animals with a "magnetic sense" by which to judge direction.

...As detailed in a new paper published online July 9 in the journal Proceedings of the National Academy of Sciences, the researchers found that the magnetic cells in the trout's noses swayed in response to a magnetic field 100 times more forcefully than had previously been predicted. "More importantly, we show for the first time that the internal compass needle has a strong connection to the plasma membrane [or outer membrane] of the cell, which is important to realize an immediate sensing process," said lead researcher Michael Winklhofer of the University of Munich in Germany.
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