by Brian Thomas, M.S. *
How does the salmon find its way from the big, wide ocean to the same stream, hundreds of miles away to the exact same spawning ground of its birth? Studies have shown that the fish use their acute sense of smell to navigate, whereby chemoreceptor cells in their noses detect specific chemicals. Other studies have shown that salmon and other animals somehow also use an internal compass. Researchers have finally discovered it.
The salmon compasses were hard to find because they are so small. Individual cells contain microscopic clusters of magnetite crystals, the same mineral used in hand-held compasses. Scientists isolated them from salmon nose tissue cells and observed them under a microscope. Rotating a larger magnetic field around the tissues caused only the magnetic cells to rotate in sync. They wrote in the Proceedings of the National Academy of Sciences, “The cells were observed to rotate at the same frequency as the driving frequency of the external magnetic field.”1
Apparently, the cells surrounding the magnetite-containing cells detect and transmit the angle of rotation data to sensory nerves that lead toward the fish brain. The brain coordinates combined chemical, magnetic, and other information, enabling the fish to successfully navigate.
Further, only one in 10,000 of the fish’s nasal tissue cells were magnetite-containing magnetoreceptors. Senior author of the study, Michael Winklhofer of Ludwig-Maximilians-University in Munich, told Live Science, “If they were as closely packed as photoreceptor cells in the retina or as hair cells in the inner ear, then they would interfere strongly with each other, because their internal compass needles would produce a locally strong magnetic field, which would be felt by the neighboring magnetic cells. Such proximity would deteriorate the magnetic sense.”2….
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