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No. 84: Nov-Dec 1992

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The Hunt For The Magnetoreceptor

When magnetite particles were found in organisms from bacteria to bats, it was assumed that here was the long sought magnetoreceptor which animals used for magnetic navigation. But so far, biologists do not have the slightest notion how such magnetite particles can be turned into a "magnetic sense," which sends the brain information on the direction of the geomagnetic field or, perhaps, draws a magnetic map of sorts.

A completely different sort of magnetreceptor is now under investigation, one that humans may also unknowingly possess. It utilizes special photoreceptors that employ an electron-spin resonance process which is modulated by the geomagnetic field. Some of our very sensitive magnetometers use similar phenomena. The biological version of such a receptor would be connected to the brain, as the eye is, and send signals as to the direction of the earth's magnetic field.

Sounds interesting, but is there any basis for thinking such a sophisticated gadget could have evolved? It seems that some experiments with newts by J.B. Phillips and S.C. Borland support the idea. The newts were first trained to orient themselves in a certain direction with respect to the geomagnetic field.

"When tested under one of four artificial field alignments (magnetic north at geographic north, east, south or west), the newts kept their training directions constant relative to the magnetic rather than the geographic system of reference, but they selected different angles with respect to the magnetic field when they were illuminated by either short (about 450 nm) or long-wavelength light (about 500 nm). When tested under 475-nm light, or in the dark, they were completely disoriented."

The experiments demonstrated that light was crucial to the newts' magnetic sense, and that photoreceptors had to be involved.

(Wehner, Reudiger; "Hunt for the Magnetoreceptor," Nature, 359: 105, 1992.)

From Science Frontiers #84, NOV-DEC 1992. 1992-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:

Quotes

  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987