scholarly journals Broadband 75–85 MHz radiofrequency fields disrupt magnetic compass orientation in night-migratory songbirds consistent with a flavin-based radical pair magnetoreceptor

2022 ◽  
Author(s):  
Bo Leberecht ◽  
Dmitry Kobylkov ◽  
Thiemo Karwinkel ◽  
Sara Döge ◽  
Lars Burnus ◽  
...  
Keyword(s):  
Radical Pair ◽  
Hyperfine Interactions ◽  
Magnetic Compass ◽  
Nuclear Spins ◽  
Compass Orientation ◽  
Migratory Songbirds ◽  
Migratory Songbird ◽  
Behavioural Experiments ◽  
A Chain

AbstractThe light-dependent magnetic compass sense of night-migratory songbirds can be disrupted by weak radiofrequency fields. This finding supports a quantum mechanical, radical-pair-based mechanism of magnetoreception as observed for isolated cryptochrome 4, a protein found in birds’ retinas. The exact identity of the magnetically sensitive radicals in cryptochrome is uncertain in vivo, but their formation seems to require a bound flavin adenine dinucleotide chromophore and a chain of four tryptophan residues within the protein. Resulting from the hyperfine interactions of nuclear spins with the unpaired electrons, the sensitivity of the radicals to radiofrequency magnetic fields depends strongly on the number of magnetic nuclei (hydrogen and nitrogen atoms) they contain. Quantum-chemical calculations suggested that electromagnetic noise in the frequency range 75–85 MHz could give information about the identity of the radicals involved. Here, we show that broadband 75–85 MHz radiofrequency fields prevent a night-migratory songbird from using its magnetic compass in behavioural experiments. These results indicate that at least one of the components of the radical pair involved in the sensory process of avian magnetoreception must contain a substantial number of strong hyperfine interactions as would be the case if a flavin–tryptophan radical pair were the magnetic sensor.

scholarly journals A novel isoform of cryptochrome 4 (Cry4b) is expressed in the retina of a night-migratory songbird

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Angelika Einwich ◽  
Karin Dedek ◽  
Pranav Kumar Seth ◽  
Sascha Laubinger ◽  
Henrik Mouritsen
Keyword(s):  
Mrna Expression ◽  
Expression Pattern ◽  
Migratory Birds ◽  
Radical Pair ◽  
The Novel ◽  
Erithacus Rubecula ◽  
Compass Orientation ◽  
Additional Exon ◽  
Magnetic Compass Orientation ◽  
Migratory Songbird

Abstract The primary sensory molecule underlying light-dependent magnetic compass orientation in migratory birds has still not been identified. The cryptochromes are the only known class of vertebrate proteins which could mediate this mechanism in the avian retina. Cryptochrome 4 of the night-migratory songbird the European robin (Erithacus rubecula; erCry4) has several of the properties needed to be the primary magnetoreceptor in the avian eye. Here, we report on the identification of a novel isoform of erCry4, which we named erCry4b. Cry4b includes an additional exon of 29 amino acids compared to the previously described form of Cry4, now called Cry4a. When comparing the retinal circadian mRNA expression pattern of the already known isoform erCry4a and the novel erCry4b isoform, we find that erCry4a is stably expressed throughout day and night, whereas erCry4b shows a diurnal mRNA oscillation. The differential characteristics of the two erCry4 isoforms regarding their 24-h rhythmicity in mRNA expression leads us to suggest that they might have different functions. Based on the 24-h expression pattern, erCry4a remains the more likely cryptochrome to be involved in radical-pair-based magnetoreception, but at the present time, an involvement of erCry4b cannot be excluded.

scholarly journals Light-dependent magnetoreception in birds: the crucial step occurs in the dark

2016 ◽  
Vol 13 (118) ◽  
pp. 20151010 ◽  
Author(s):  
Roswitha Wiltschko ◽  
Margaret Ahmad ◽  
Christine Nießner ◽  
Dennis Gehring ◽  
Wolfgang Wiltschko
Keyword(s):  
Magnetic Field ◽  
Flavin Adenine Dinucleotide ◽  
Radical Pair ◽  
Magnetic Compass ◽  
Radical Pairs ◽  
Intermittent Light ◽  
Pair Model ◽  
Dark Interval ◽  
Behavioural Experiments ◽  
The Magnetic Field

The Radical Pair Model proposes that the avian magnetic compass is based on spin-chemical processes: since the ratio between the two spin states singlet and triplet of radical pairs depends on their alignment in the magnetic field, it can provide information on magnetic directions. Cryptochromes, blue light-absorbing flavoproteins, with flavin adenine dinucleotide as chromophore, are suggested as molecules forming the radical pairs underlying magnetoreception. When activated by light, cryptochromes undergo a redox cycle, in the course of which radical pairs are generated during photo-reduction as well as during light-independent re-oxidation. This raised the question as to which radical pair is crucial for mediating magnetic directions. Here, we present the results from behavioural experiments with intermittent light and magnetic field pulses that clearly show that magnetoreception is possible in the dark interval, pointing to the radical pair formed during flavin re-oxidation. This differs from the mechanism considered for cryptochrome signalling the presence of light and rules out most current models of an avian magnetic compass based on the radical pair generated during photo-reduction. Using the radical pair formed during re-oxidation may represent a specific adaptation of the avian magnetic compass.

scholarly journals Electromagnetic 0.1–100 kHz noise does not disrupt orientation in a night-migrating songbird implying a spin coherence lifetime of less than 10 µs

2019 ◽  
Vol 16 (161) ◽  
pp. 20190716 ◽  
Author(s):  
Dmitry Kobylkov ◽  
Joe Wynn ◽  
Michael Winklhofer ◽  
Raisa Chetverikova ◽  
Jingjing Xu ◽  
...  
Keyword(s):  
Electromagnetic Fields ◽  
Migratory Birds ◽  
Radical Pair ◽  
Coherence Time ◽  
Magnetic Compass ◽  
Radio Waves ◽  
Spin Coherence ◽  
Compass Orientation ◽  
Magnetic Compass Orientation ◽  
Migrating Birds

According to the currently prevailing theory, the magnetic compass sense in night-migrating birds relies on a light-dependent radical-pair-based mechanism. It has been shown that radio waves at megahertz frequencies disrupt magnetic orientation in migratory birds, providing evidence for a quantum-mechanical origin of the magnetic compass. Still, many crucial properties, e.g. the lifetime of the proposed magnetically sensitive radical pair, remain unknown. The current study aims to estimate the spin coherence time of the radical pair, based on the behavioural responses of migratory birds to broadband electromagnetic fields covering the frequency band 0.1–100 kHz. A finding that the birds were unable to use their magnetic compass under these conditions would imply surprisingly long-lived (greater than 10 µs) spin coherence. However, we observed no effect of 0.1–100 kHz radiofrequency (RF) fields on the orientation of night-migratory Eurasian blackcaps ( Sylvia atricapilla ). This suggests that the lifetime of the spin coherence involved in magnetoreception is shorter than the period of the highest frequency RF fields used in this experiment (i.e. approx. 10 µs). This result, in combination with an earlier study showing that 20–450 kHz electromagnetic fields disrupt magnetic compass orientation, suggests that the spin coherence lifetime of the magnetically sensitive radical pair is in the range 2–10 µs.

scholarly journals Navigating at night: fundamental limits on the sensitivity of radical pair magnetoreception under dim light

2019 ◽  
Vol 52 ◽  
Author(s):  
H. G. Hiscock ◽  
T. W. Hiscock ◽  
D. R. Kattnig ◽  
T. Scrivener ◽  
A. M. Lewis ◽  
...  
Keyword(s):  
Radical Pair ◽  
Photoreceptor Cells ◽  
Low Light ◽  
Radical Pairs ◽  
Fundamental Limits ◽  
Short Supply ◽  
Light Levels ◽  
Migratory Songbirds ◽  
Open Question

Abstract Night-migratory songbirds appear to sense the direction of the Earth's magnetic field via radical pair intermediates formed photochemically in cryptochrome flavoproteins contained in photoreceptor cells in their retinas. It is an open question whether this light-dependent mechanism could be sufficiently sensitive given the low-light levels experienced by nocturnal migrants. The scarcity of available photons results in significant uncertainty in the signal generated by the magnetoreceptors distributed around the retina. Here we use results from Information Theory to obtain a lower bound estimate of the precision with which a bird could orient itself using only geomagnetic cues. Our approach bypasses the current lack of knowledge about magnetic signal transduction and processing in vivo by computing the best-case compass precision under conditions where photons are in short supply. We use this method to assess the performance of three plausible cryptochrome-derived flavin-containing radical pairs as potential magnetoreceptors.

scholarly journals Night-migratory garden warblers can orient with their magnetic compass using the left, the right or both eyes

2009 ◽  
Vol 7 (suppl_2) ◽  
Author(s):  
Christine Maira Hein ◽  
Manuela Zapka ◽  
Dominik Heyers ◽  
Sandra Kutzschbauch ◽  
Nils-Lasse Schneider ◽  
...  
Keyword(s):  
Magnetic Compass ◽  
Compass Orientation ◽  
Orientation Behaviour ◽  
Eyes Open ◽  
Magnetic Compass Orientation ◽  
Migratory Songbird ◽  
Sylvia Borin ◽  
The Right

Several studies have suggested that the magnetic compass of birds is located only in the right eye. However, here we show that night-migrating garden warblers ( Sylvia borin ) are able to perform magnetic compass orientation with both eyes open, with only the left eye open and with only the right eye open. We did not observe any clear lateralization of magnetic compass orientation behaviour in this migratory songbird, and, therefore, it seems that the suggested all-or-none lateralization of magnetic compass orientation towards the right eye only cannot be generalized to all birds, and that the answer to the question of whether magnetic compass orientation in birds is lateralized is probably not as simple as suggested previously.

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 A magnet attached to the forehead disrupts magnetic compass orientation in a migratory songbird

2021 ◽  
Author(s):  
Florian Packmor ◽  
Dmitry Kishkinev ◽  
Flora Bittermann ◽  
Barbara Kofler ◽  
Clara Machowetz ◽  
...  
Keyword(s):  
Bird Species ◽  
Magnetic Compass ◽  
Disruptive Effect ◽  
Free Flight ◽  
Compass Orientation ◽  
Experimental Conditions ◽  
Magnetic Compass Orientation ◽  
Orientation Cues ◽  
Migratory Songbird ◽  
Small Bird

For studies on magnetic compass orientation and navigation performance in small bird species, controlled experiments with orientation cages inside an electromagnetic coil system are the most prominent methodological paradigm. These are, however, not applicable when studying larger bird species and/or orientation behaviour during free flight. For this, researchers have followed a very different approach. By attaching small magnets to birds, they intended to deprive them of access to meaningful magnetic information. Unfortunately, results from studies using this approach appear rather inconsistent. As these are based on experiments with birds under free flight conditions, which usually do not allow exclusion of other potential orientation cues, an assessment of the overall efficacy of this approach is difficult to conduct. Here, we directly test the efficacy of small magnets for temporarily disrupting magnetic compass orientation in small migratory songbirds using orientation cages under controlled experimental conditions. We found that birds which have access to the Earth's magnetic field as their sole orientation cue show a general orientation towards their seasonally appropriate migratory direction. When carrying magnets on their forehead under these conditions, the same birds become disoriented. However, under changed conditions that allow birds access to other (i.e. celestial) orientation cues, any disruptive effect of the magnets they carry appears obscured. Our results provide clear evidence for the efficacy of the magnet approach for temporarily disrupting magnetic compass orientation in birds, but also reveal its limitations for application in experiments under free flight conditions.

Auditory and Magnetic Compass Orientation in C57BL/6 mice

2006 ◽  
Author(s):  
John B. Phillips ◽  
R. Muheim ◽  
N. M. Edgar ◽  
K. S. Sloan
Keyword(s):  
Magnetic Compass ◽  
Compass Orientation ◽  
Magnetic Compass Orientation
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