RAINBOW trout can 鈥渟mell鈥� the difference between north and south.
Biologists in New Zealand have discovered a magnetic compass in their
noses.
Many animals, including birds, reptiles and some mammals, can orient
themselves relative to the Earth鈥檚 magnetic field. But north-sensing cells,
believed to rely on the magnetic mineral magnetite, have never been
identified.
Michael Walker and his colleagues at the University of Auckland report in
Nature (vol 390, p 371) that they found a facial nerve fibre in trout that fires
in the presence of a magnetic field. By injecting the fibre with dye, they
traced it back to nerve cells in the fish鈥檚 nose that contain magnetite.
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