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First published online October 16, 2009
Journal of Experimental Biology 212, 3473-3477 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.028670

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Radio frequency magnetic fields disrupt magnetoreception in American cockroach

Martin Vácha^*, Tereza Pová and Markéta Kvíalová

Department of Animal Physiology and Immunology, Faculty of Science, Masaryk University, Brno, Kotlárská 2, 611 37, Brno, Czech Republic

^* Author for correspondence (vacha{at}sci.muni.cz)

Accepted 21 July 2009

The sense that allows birds to orient themselves by the Earth's magnetic field can be disabled by an oscillating magnetic field whose intensity is just a fraction of the geomagnetic field intensity and whose oscillations fall into the medium or high frequency radio wave bands. This remarkable phenomenon points very clearly at one of two existing alternative magnetoreception mechanisms in terrestrial animals, i.e. the mechanism based on the radical pair reactions of specific photosensitive molecules. As the first such study in invertebrates, our work offers evidence that geomagnetic field reception in American cockroach is sensitive to a weak radio frequency field. Furthermore, we show that the `deafening' effect at Larmor frequency 1.2 MHz is stronger than at different frequencies. The parameter studied was the rise in locomotor activity of cockroaches induced by periodic changes in the geomagnetic North positions by 60 deg. The onset of the disruptive effect of a 1.2 MHz field was found between 12 nT and 18 nT whereas the threshold of a doubled frequency field 2.4 MHz fell between 18 nT and 44 nT. A 7 MHz field showed no impact even in maximal 44 nT magnetic flux density. The results indicate resonance effects rather than non-specific bias of procedure itself and suggest that insects may be equipped with the same magnetoreception system as the birds.

Key words: magnetoreception, insects, radical pair, radio frequency, cryptochrome

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