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 Magnetic field effects as a result of the radical pair mechanism are unlikely in redox enzymes

2015 ◽  
Vol 12 (103) ◽  
pp. 20141155 ◽  
Author(s):  
Hanan L. Messiha ◽  
Thanyaporn Wongnate ◽  
Pimchai Chaiyen ◽  
Alex R. Jones ◽  
Nigel S. Scrutton
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Radical Pair ◽  
Radical Pair Mechanism ◽  
Magnetic Field Effects ◽  
Experimental Conditions ◽  
Flow Measurements ◽  
Field Sensitivity ◽  
Biochemical Systems ◽  
The Magnetic Field

Environmental exposure to electromagnetic fields is potentially carcinogenic. The radical pair mechanism is considered the most feasible mechanism of interaction between weak magnetic fields encountered in our environment and biochemical systems. Radicals are abundant in biology, both as free radicals and reaction intermediates in enzyme mechanisms. The catalytic cycles of some flavin-dependent enzymes are either known or potentially involve radical pairs. Here, we have investigated the magnetic field sensitivity of a number of flavoenzymes with important cellular roles. We also investigated the magnetic field sensitivity of a model system involving stepwise reduction of a flavin analogue by a nicotinamide analogue—a reaction known to proceed via a radical pair. Under the experimental conditions used, magnetic field sensitivity was not observed in the reaction kinetics from stopped-flow measurements in any of the systems studied. Although widely implicated in radical pair chemistry, we conclude that thermally driven, flavoenzyme-catalysed reactions are unlikely to be influenced by exposure to external magnetic fields.

scholarly journals Avian magnetic compass can be tuned to anomalously low magnetic intensities

2013 ◽  
Vol 280 (1763) ◽  
pp. 20130853 ◽  
Author(s):  
Michael Winklhofer ◽  
Evelyn Dylda ◽  
Peter Thalau ◽  
Wolfgang Wiltschko ◽  
Roswitha Wiltschko
Keyword(s):  
Magnetic Field ◽  
Exposure Time ◽  
Geomagnetic Field ◽  
Magnetic Compass ◽  
Radical Pair Mechanism ◽  
Compass Orientation ◽  
Directional Information ◽  
Total Exposure Time ◽  
Magnetic Compass Orientation ◽  
Local Intensity

The avian magnetic compass works in a fairly narrow functional window around the intensity of the local geomagnetic field, but adjusts to intensities outside this range when birds experience these new intensities for a certain time. In the past, the geomagnetic field has often been much weaker than at present. To find out whether birds can obtain directional information from a weak magnetic field, we studied spontaneous orientation preferences of migratory robins in a 4 µT field (i.e. a field of less than 10 per cent of the local intensity of 47 µT). Birds can adjust to this low intensity: they turned out to be disoriented under 4 µT after a pre-exposure time of 8 h to 4 µT, but were able to orient in this field after a total exposure time of 17 h. This demonstrates a considerable plasticity of the avian magnetic compass. Orientation in the 4 µT field was not affected by local anaesthesia of the upper beak, but was disrupted by a radiofrequency magnetic field of 1.315 MHz, 480 nT, suggesting that a radical-pair mechanism still provides the directional information in the low magnetic field. This is in agreement with the idea that the avian magnetic compass may have developed already in the Mesozoic in the common ancestor of modern birds.

USE OF A SPECIALIZED MAGNETORECEPTION SYSTEM FOR HOMING BY THE EASTERN RED-SPOTTED NEWT NOTOPHTHALMUS VIRIDESCENS

1994 ◽  
Vol 188 (1) ◽  
pp. 275-291 ◽  
Author(s):  
J Phillips ◽  
S Borland
Keyword(s):  
Magnetic Field ◽  
Short Wavelength ◽  
Magnetic Compass ◽  
Compass Orientation ◽  
Full Spectrum ◽  
Long Wavelength ◽  
Magnetic Compass Orientation ◽  
Short Wavelength Light ◽  
The Magnetic Field ◽  
Wavelength Light

Laboratory experiments were carried out to investigate the effects of varying the wavelength of light on the use of an earth-strength magnetic field for shoreward orientation and for the compass component of homing. In the earlier shoreward orientation experiments, newts tested under full-spectrum and short-wavelength (i.e. 400 and 450 nm) light exhibited shoreward magnetic compass orientation. Under long-wavelength (i.e. 550 and 600 nm) light, newts exhibited magnetic compass orientation that was rotated 90 ° counterclockwise to the shoreward direction. This wavelength-dependent shift in magnetic compass orientation was shown to be due to a direct effect of light on the underlying magnetoreception mechanism. In homing experiments, newts tested under full-spectrum and short-wavelength light exhibited homeward magnetic compass orientation. Under long-wavelength light, newts were randomly distributed with respect to the magnetic field. The different effects of long-wavelength light on shoreward orientation and homing confirmed earlier evidence that different magnetoreception systems mediate these two forms of orientation behaviour. The properties of the newt's homing response are consistent with the use of a hybrid magnetoreception system receiving inputs from the light-dependent magnetic compass and from a non-light-dependent intensity (or inclination) detector which, unlike the compass, is sensitive to the polarity of the magnetic field.

Lateralisation of magnetic compass orientation in silvereyes, Zosterops lateralis

2003 ◽  
Vol 51 (6) ◽  
pp. 597 ◽  
Author(s):  
Wolfgang Wiltschko ◽  
Ursula Munro ◽  
Hugh Ford ◽  
Roswitha Wiltschko
Keyword(s):  
Geomagnetic Field ◽  
Magnetic Compass ◽  
Compass Orientation ◽  
Directional Information ◽  
Zosterops Lateralis ◽  
Magnetic Compass Orientation ◽  
Directional Preference ◽  
The Right ◽  
The Brain ◽  
The Magnetic Field

The ability of migratory silvereyes to orient was tested in the geomagnetic field with one eye covered. Silvereyes using only their right eye were able to orient in migratory direction just as well as birds using both eyes. Using only their left eye, however, the birds did not show a significant directional preference. These data indicate that directional information from the magnetic field is mediated almost exclusively by the right eye and processed by the left hemisphere of the brain. Together with corresponding findings from European robins and indications for a similar phenomenon in homing pigeons, they suggest that a strong lateralisation of the magnetic compass is widespread among birds.

Time-resolved studies of radical pairs

2009 ◽  
Vol 37 (2) ◽  
pp. 358-362 ◽  
Author(s):  
Jonathan R. Woodward ◽  
Timothy J. Foster ◽  
Alex R. Jones ◽  
Adrian T. Salaoru ◽  
Nigel S. Scrutton
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Chemical Reactions ◽  
Radical Pair ◽  
Radical Pair Mechanism ◽  
Magnetic Field Effects ◽  
Radical Pairs ◽  
Time Resolved ◽  
Field Effects ◽  
Field Sensitivity

The effect of magnetic fields on chemical reactions through the RP (radical pair) mechanism is well established, but there are few examples, in the literature, of biological reactions that proceed through RP intermediates and show magnetic field-sensitivity. The present and future relevance of magnetic field effects in biological reactions is discussed.

scholarly journals Radical pairs may play a role in microtubule reorganization

2021 ◽  
Author(s):  
Hadi ZADEH-HAGHIGHI ◽  
Christoph Simon
Keyword(s):  
Magnetic Field ◽  
Radical Pair ◽  
Spin Dynamics ◽  
Radical Pair Mechanism ◽  
Magnetic Field Effects ◽  
Radical Pairs ◽  
Quantum Theories ◽  
Mechanism Model ◽  
Field Effects ◽  
Isotopic Dependence

The exact mechanism behind general anesthesia remains an open question in neuroscience. It has been proposed that anesthetics selectively prevent consciousness and memory via acting on microtubules (MTs). It is known that the magnetic field modulates MT organization. A recent study shows that a radical pair model can explain the isotope effect in xenon-induced anesthesia and predicts magnetic field effects on anesthetic potency. Further, reactive oxygen species are also implicated in MT stability and anesthesia. Based on a simple radical pair mechanism model and a simple mathematical model of MT organization, we show that magnetic fields can modulate spin dynamics of naturally occurring radical pairs in MT. We show that the spin dynamics influence a rate in the reaction cycle, which translates into a change in the MT density. We can reproduce magnetic field effects on the MT concentration that have been observed. Our model also predicts additional effects at slightly higher fields. Our model further predicts that the effect of zinc on the MT density exhibits isotopic dependence. The findings of this work make a connection between microtubule-based and radical pair-based quantum theories of consciousness.

Magnetic compass orientation in the blind mole rat Spalax ehrenbergi

2001 ◽  
Vol 204 (4) ◽  
pp. 751-758 ◽  
Author(s):  
T. Kimchi ◽  
J. Terkel
Keyword(s):  
Magnetic Field ◽  
Magnetic Compass ◽  
Food Store ◽  
Earth’S Magnetic Field ◽  
Compass Orientation ◽  
Spalax Ehrenbergi ◽  
Mole Rat ◽  
Earth's Magnetic Field ◽  
Magnetic Compass Orientation ◽  
Directional Preference

The blind mole rat Spalax ehrenbergi is a solitary, subterranean rodent that digs and inhabits a system of branching tunnels, with no above-ground exits, which it never leaves unless forced to. To survive, the mole rat must be able to orient efficiently in its tunnel system. The sensory channels available for spatial orientation in the subterranean environment are restricted in comparison with those existing above ground. This study examined the possibility that the mole rat is able to perceive and use the earth's magnetic field to orient in space. Experiments were performed using a device constructed from a pair of electromagnetic ‘Helmholtz coils’, which create a magnetic field whose direction and strength can be altered. In the first experiment, we tested a group of mole rats (N=33) in an eight-armed maze under the earth's natural magnetic field to determine whether they have directional preferences for the location of their sleeping nest, food chamber and toilet site. A second group of mole rats (N=30) was tested for their directional preference after the earth's magnetic field had been experimentally shifted by 180 degrees. We found that the first group exhibited a significant preference (P<0.001) to build both their sleeping nest and their food store in the southern sector of the maze, whereas the second group shifted the location of their nests (P<0.01) and food store (P<0.05), to the northern sector of the maze, corresponding to the shift in the magnetic field. In the second experiment, we tested whether the magnetic compass orientation found in the first experiment depends on a light stimulus by testing a group of mole rats in the eight-armed maze under total darkness. No significant difference in directional preference between light and dark test conditions was observed. It can be concluded, therefore, that, in contrast to some amphibians and birds, magnetic compass orientation in the mole rat is independent of light stimulation. In the third experiment, we examined whether mole rats (N=24) use the earth's magnetic field as a compass cue to orient in a labyrinth. In the first stage (trials 1–13), the animals were trained to reach a goal box at the end of a complex labyrinth until all individuals had learned the task. In the second stage (trial 14), half the trained mole rats underwent another labyrinth trial under the earth's natural magnetic field, while the other half were tested under a magnetic field shifted by 180 degrees. We found a significant decrease (P<0.001) in performance of the mole rats tested under the shifted magnetic field compared with the group tested under the natural magnetic field. The findings from these experiments prove that the mole rat is able to perceive and use the earth's magnetic field to orient in space.

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