ID Number		2182
Study Type		In Vivo
Model		0.1-10 MHz exposure to birds and analysis of migratory behavior
Details		Migratory birds (Robins) were exposed in the lab to a 7 MHz or broadband 0.1-10 MHz field (in addition to the normal geomagnetic field of the earth) and evaluated for migratory behavior. The authors report that with exposure to vertically aligned fields, the birds became disoriented in a way that depended upon the angle of the oscillating field in relation to the geomagnetic field. The authors suggest the effect may be due to an effect on the spin state of certain migratory protein molecules in the avian brain - specifically a resonance effect on singlettriplet transitions in the magnetic compass based on a radicalpair mechanism. AUTHORS' ABSTRACT: Wiltschko et al. 2015 (IEEE #5865): The avian magnetic compass, probably based on radical pair processes, works only in a narrow functional window around the local field strength, with cryptochrome 1a as most likely receptor molecule. Radio-frequency fields in the MHz range have been shown to disrupt the birds' orientation, yet the nature of this interference is still unclear. In an immuno-histological study, we tested whether the radio-frequency fields interfere with the photoreduction of cryptochrome, but this does not seem to be the case. In behavioural studies, birds were not able to adjust to radio-frequency fields like they are able to adjust to static fields outside the normal functional range: neither a 2-h pre-exposure in a 7.0 MHz field, 480 nT, nor a 7-h pre-exposure in a 1.315 MHz field, 15 nT, allowed the birds to regain their orientation ability. This inability to adjust to radio-frequency fields suggests that these fields interfere directly with the primary processes of magnetoreception and therefore disable the avian compass as long as they are present. They do not have lasting adverse after-effects, however, as birds immediately after exposure to a radio-frequency field were able to orient in the local geomagnetic field. AUTHORS' ABSTRACT: Wiltschko and Wiltschko 2005 (IEEE #6466): Animals use the geomagnetic field in many ways: the magnetic vector provides a compass; magnetic intensity and/or inclination play a role as a component of the navigational 'map', and magnetic conditions of certain regions act as 'sign posts' or triggers, eliciting specific responses. A magnetic compass is widespread among animals, magnetic navigation is indicated e.g. in birds, marine turtles and spiny lobsters and the use of magnetic 'sign posts' has been described for birds and marine turtles. For magnetoreception, two hypotheses are currently discussed, one proposing a chemical compass based on a radical pair mechanism, the other postulating processes involving magnetite particles. The available evidence suggests that birds use both mechanisms, with the radical pair mechanism in the right eye providing directional information and a magnetite-based mechanism in the upper beak providing information on position as component of the 'map'. Behavioral data from other animals indicate a light-dependent compass probably based on a radical pair mechanism in amphibians and a possibly magnetite-based mechanism in mammals. Histological and electrophysiological data suggest a magnetite-based mechanism in the nasal cavities of salmonid fish. Little is known about the parts of the brain where the respective information is processed.
Findings		Effects
Status		Completed With Publication
Principal Investigator		University of California Irvine, USA
Funding Agency		Private/Instit.
Country		UNITED STATES
References		Ritz, T et al. Nature, (2004) 429:177-180 Wiltschko , R et al. J Royal Society Interface., (2015) 12:20141103- Wiltschko, W et al. J Comp Physiol A Neuroethol Sens Neural Behav Physiol., (2005) 191:675-693 Keary, N et al. Front Zool., (2009) 6:25-
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