Magnetic reception

Magnetic reception (biology)

Sensitivity to magnetic stimuli, especially the very weak ones occurring naturally in the environment.

Evidence of magnetic detection has been found in a variety of invertebrates, including protozoa, flatworms, snails, and insects. In 1968 Martin Lindauer and Herman Martin first published extensive data showing that the Earth's geomagnetic field influences the orientation of the waggle-run dance by which a scout honeybee communicates the distance and direction of a food source to the forager bees. Later, Lindauer and Martin showed that fluctuations of less than 10-4 gauss (roughly 1/10,000 of the Earth's field) can influence these bees' behavior. Other investigators found evidence of magnetic detection in other kinds of insects, including termites, beetles, and fruit flies (Drosophila).

Most of the evidence for magnetic detection by birds has come from studies of their migratory and homing behavior. Results strongly suggest that birds possess a magnetic compass, that is, they can determine compass bearings from the geomagnetic field. Evidence indicates that birds' sensitivity to magnetic stimuli is roughly similar to the honeybees'. It appears that the tiny fluctuations in the Earth's magnetic field caused by solar flares and other solar disturbances have a detectable effect on birds' navigation. The detection system probably has a narrow range of sensitivity; magnetic fields much stronger or weaker than the Earth's probably cannot be detected. See Migratory behavior

Although behavioral effects of magnetic stimuli have been found in many kinds of animals, no one has yet succeeded in conditioning an animal to a magnetic stimulus in the laboratory. There is abundant evidence that the detection process is not quick, usually taking 15 min or more; hence, the flash stimuli presented in most classical conditioning attempts may be undetectable.

The physical mechanism for mag­netic detection by living organisms is unknown, though a variety of possibilities have been put forward.

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