Resonance effects indicate a radical-pair mechanism for avian magnetic compass

Nature ◽  
2004 ◽  
Vol 429 (6988) ◽  
pp. 177-180 ◽  
Author(s):  
Thorsten Ritz ◽  
Peter Thalau ◽  
John B. Phillips ◽  
Roswitha Wiltschko ◽  
Wolfgang Wiltschko
Keyword(s):  
Radical Pair ◽  
Magnetic Compass ◽  
Radical Pair Mechanism ◽  
Resonance Effects

scholarly journals The magnetic compass mechanisms of birds and rodents are based on different physical principles

2006 ◽  
Vol 3 (9) ◽  
pp. 583-587 ◽  
Author(s):  
Peter Thalau ◽  
Thorsten Ritz ◽  
Hynek Burda ◽  
Regina E Wegner ◽  
Roswitha Wiltschko
Keyword(s):  
Geomagnetic Field ◽  
Migratory Birds ◽  
Radical Pair ◽  
Broad Band ◽  
Static Field ◽  
Magnetic Compass ◽  
Radical Pair Mechanism ◽  
Zeeman Frequency ◽  
Compass Mechanisms ◽  
Physical Principles

Recently, oscillating magnetic fields in the MHz-range were introduced as a useful diagnostic tool to identify the mechanism underlying magnetoreception. The effect of very weak high-frequency fields on the orientation of migratory birds indicates that the avian magnetic compass is based on a radical pair mechanism. To analyse the nature of the magnetic compass of mammals, we tested rodents, Ansell's mole-rats, using their tendency to build their nests in the southern part of the arena as a criterion whether or not they could orient. In contrast to birds, their orientation was not disrupted when a broad-band field of 0.1–10 MHz of 85 nT or a 1.315 MHz field of 480 nT was added to the static geomagnetic field of 46 000 nT. Even increasing the intensity of the 1.315 MHz field (Zeeman frequency in the local geomagnetic field) to 4800 nT, more than a tenth of the static field, the mole-rats remained unaffected and continued to build their nests in the south. These results indicate that in contrast to that of birds, their magnetic compass does not involve radical pair processes; it seems to be based on a fundamentally different principle, which probably involves magnetite.

scholarly journals Cryptochrome expression in avian UV cones: revisiting the role of CRY1 as magnetoreceptor

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Atticus Pinzon-Rodriguez ◽  
Rachel Muheim
Keyword(s):  
Zebra Finch ◽  
Migratory Birds ◽  
Radical Pair ◽  
Magnetic Compass ◽  
Radical Pair Mechanism ◽  
Type Ii ◽  
Light Activation ◽  
Functional Changes ◽  
Circadian Expression

AbstractCryptochromes (CRY) have been proposed as putative magnetoreceptors in vertebrates. Localisation of CRY1 in the UV cones in the retinas of birds suggested that it could be the candidate magnetoreceptor. However, recent findings argue against this possibility. CRY1 is a type II cryptochrome, a subtype of cryptochromes that may not be inherently photosensitive, and it exhibits a clear circadian expression in the retinas of birds. Here, we reassessed the localisation and distribution of CRY1 in the retina of the zebra finch. Zebra finches have a light-dependent magnetic compass based on a radical-pair mechanism, similar to migratory birds. We found that CRY1 colocalised with the UV/V opsin (SWS1) in the outer segments of UV cones, but restricted to the tip of the segments. CRY1 was found in all UV cones across the entire retina, with the highest densities near the fovea. Pre-exposure of birds to different wavelengths of light did not result in any difference in CRY1 detection, suggesting that CRY1 did not undergo any detectable functional changes as result of light activation. Considering that CRY1 is likely not involved in magnetoreception, our findings open the possibility for an involvement in different, yet undetermined functions in the avian UV/V cones.

scholarly journals Polarized light modulates light-dependent magnetic compass orientation in birds

2016 ◽  
Vol 113 (6) ◽  
pp. 1654-1659 ◽  
Author(s):  
Rachel Muheim ◽  
Sissel Sjöberg ◽  
Atticus Pinzon-Rodriguez
Keyword(s):  
Magnetic Field ◽  
Radical Pair ◽  
Polarized Light ◽  
Magnetic Compass ◽  
Radical Pair Mechanism ◽  
Magnetic Field Effects ◽  
Compass Orientation ◽  
Magnetic Compass Orientation ◽  
Avian Retina ◽  
The Magnetic Field

Magnetoreception of the light-dependent magnetic compass in birds is suggested to be mediated by a radical-pair mechanism taking place in the avian retina. Biophysical models on magnetic field effects on radical pairs generally assume that the light activating the magnetoreceptor molecules is nondirectional and unpolarized, and that light absorption is isotropic. However, natural skylight enters the avian retina unidirectionally, through the cornea and the lens, and is often partially polarized. In addition, cryptochromes, the putative magnetoreceptor molecules, absorb light anisotropically, i.e., they preferentially absorb light of a specific direction and polarization, implying that the light-dependent magnetic compass is intrinsically polarization sensitive. To test putative interactions between the avian magnetic compass and polarized light, we developed a spatial orientation assay and trained zebra finches to magnetic and/or overhead polarized light cues in a four-arm “plus” maze. The birds did not use overhead polarized light near the zenith for sky compass orientation. Instead, overhead polarized light modulated light-dependent magnetic compass orientation, i.e., how the birds perceive the magnetic field. Birds were well oriented when tested with the polarized light axis aligned parallel to the magnetic field. When the polarized light axis was aligned perpendicular to the magnetic field, the birds became disoriented. These findings are the first behavioral evidence to our knowledge for a direct interaction between polarized light and the light-dependent magnetic compass in an animal. They reveal a fundamentally new property of the radical pair-based magnetoreceptor with key implications for how birds and other animals perceive the Earth’s magnetic field.

scholarly journals Cryptochrome Expression in Avian UV Cones: Revisiting the Role of Cry1 As Magnetoreceptor

2020 ◽  
Author(s):  
Atticus Pinzon-Rodriguez ◽  
Rachel Muheim
Keyword(s):  
Zebra Finch ◽  
Migratory Birds ◽  
Radical Pair ◽  
Magnetic Compass ◽  
Radical Pair Mechanism ◽  
Type Ii ◽  
Light Activation ◽  
Functional Changes ◽  
Circadian Expression

Abstract Cryptochromes (Cry) have been proposed as putative magnetoreceptors in vertebrates. Localisation of Cry1 in the UV cones in the retinas of birds suggested that it could be the candidate magnetoreceptor. However, recent findings argue against this possibility. Cry1 is a type II cryptochrome, a subtype of cryptochromes that may not be inherently photosensitive, and it exhibits a clear circadian expression in the retinas of birds. Here, we reassessed the localization and distribution of Cry1 in the retina of the zebra finch. Zebra finches have a light-dependent magnetic compass based on a radical-pair mechanism, similar to migratory birds. We found that Cry1 colocalized with the UV/V opsin (SWS1) in the outer segments of UV cones, but restricted to the tip of the segments. Cry1 was expressed in all UV cones across the entire retina, with the highest densities near the fovea. Pre-exposure of birds to different wavelengths of light did not result in any difference in Cry1 expression, suggesting that Cry1 did not undergo any detectable functional changes as result of light activation. Considering that Cry1 is likely not involved in magnetoreception, our findings open the possibility for an involvement in different, yet undetermined functions in the avian UV/V cones.

Application of the radical pair mechanism to free radicals in organized systems: Can the effects of 60 Hz be predicted from studies under static fields?

1994 ◽  
Vol 15 (6) ◽  
pp. 549-554 ◽  
Author(s):  
J. C. Scaiano ◽  
N. Mohtat ◽  
F. L. Cozens ◽  
J. McLean ◽  
A. Thansandote
Keyword(s):  
Free Radicals ◽  
Radical Pair ◽  
Radical Pair Mechanism

scholarly journals Could radical pairs play a role in xenon-induced general anesthesia?

2020 ◽  
Author(s):  
Jordan Smith ◽  
Hadi Zadeh Haghighi ◽  
Christoph Simon
Keyword(s):  
General Anesthesia ◽  
Radical Pair ◽  
The Body ◽  
Radical Pair Mechanism ◽  
General Anesthetic ◽  
Radical Pairs ◽  
Naturally Occurring ◽  
Isotopic Dependence ◽  
Anesthetic Potency ◽  
Recombination Dynamics

ABSTRACTUnderstanding the mechanisms underlying anesthesia would be a key step towards understanding consciousness. The process of xenon-induced general anesthesia has been shown to involve electron transfer, and the potency of xenon as a general anesthetic exhibits isotopic dependence. We propose that these observations can be explained by a mechanism in which the xenon nuclear spin influences the recombination dynamics of a naturally occurring radical pair of electrons. We develop a simple model inspired by the body of work on the radical-pair mechanism in cryptochrome in the context of avian magnetoreception, and we show that our model can reproduce the observed isotopic dependence of the general anesthetic potency of xenon in mice. Our results are consistent with the idea that radical pairs of electrons with entangled spins could be important for consciousness.

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