Radio frequency magnetic fields disrupt magnetoreception in American cockroach

Abstract

SUMMARYThe 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.

Spin-locking in low-frequency reaction yield detected magnetic resonance

“…These studies provide only a qualitative indication of the RF response: either the RF field produces a statistically significant response or it does not, making it difficult to verify that the observed effects arise from a radical pair mechanism. Attempts have been made to prove a resonance response by finding the threshold RF field strength when on and off resonance with a static field: 30,31 based on the spin-locking phenomena we now propose a definitive test. Applying an on-resonance RF field orthogonal to the static field we can expect an RF response to appear when a threshold RF field strength is exceeded and that this response will disappear again at a higher RF field strength as the radical pair becomes spin-locked and the net RF effect decreases as B 0 1 is approached.…”

“…A number of in vivo RY-DMR studies have been carried out on birds [28][29][30] and insects 31 in order to determine the origin of their magnetic sensitivity. These studies provide only a qualitative indication of the RF response: either the RF field produces a statistically significant response or it does not, making it difficult to verify that the observed effects arise from a radical pair mechanism.…”

A behavioral perspective on the biophysics of the light-dependent magnetic compass: a link between directional and spatial perception?

“…Evidence for a RPM-based magnetic compass in some animals includes: (1) sensitivity to the axis, but not polarity, of the magnetic field ( Fig.1) (Wiltschko and Wiltschko, 1972;Phillips, 1986); (2) involvement of a light-dependent magnetoreception mechanism (Phillips and Borland, 1992a;Phillips and Borland, 1992b;Phillips and Sayeed, 1993;Freake and Phillips, 2005;Wiltschko and Wiltschko, 2005;Vacha et al, 2008b); (3) disruption of magnetic compass orientation outside a narrow window of static field intensities ; (4) the absence of an effect of 'pulse remagnetization' (Beason and Semm, 1996;Munro et al, 1997a;Munro et al, 1997b); and (5) disruption by low-level alternating fields (~0.1% of the static field strength) in the low RF range (<100MHz) that should alter the magnetic field-dependent populations of singlet and triplet energy states in a RPM (Ritz et al, 2004;Ritz et al, 2009;Henbest et al, 2004;Thalau et al, 2005;Vacha et al, 2009). In migratory birds, the effects of low-level RF fields have been shown to depend on both the intensity and relative alignment of the static magnetic field (Ritz et al, 2004;Ritz et al, 2009) .…”

“…Ritz et al, 2004;Henbest et al, 2004;Thalau et al, 2005;Ritz et al, 2009;Vacha et al, 2009) has important implications for designing experiments to investigate the role of magnetic cues in rodent spatial behavior. In a study of migratory birds exposed to a RF field tuned to the Larmor frequency (the precession frequency of the magnetic moment of an electron around an external field), Ritz et al (Ritz et al, 2009) found that magnetic compass orientation was disrupted at an intensity of 15nT but not 5nT, which roughly bracketed background levels of ambient radio frequency interference (RFI); for comparison, the geomagnetic field is ~50,000nT.…”

The magnetic orientation of the Antarctic amphipod Gondogeneia antarctica is cancelled by very weak radiofrequency fields

“…The magnetoreception of insects and some mammals has also been shown to be sensitive to RF bias (Vacha et al, 2009;Malkemper et al, 2015, respectively), while mole-rats (Thalau et al, 2006) did not react to an RF field. The opportunity to investigate amphipod magnetic orientation in an Antarctic ecosystem devoid of electromagnetic noise sources led us to two main questions: (1) is there any disruptive effect of RF fields on the magnetosensitivity of marine isopods; and if so, (2) what is the RF field flux density threshold?…”