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John B Phillips - One of the best experts on this subject based on the ideXlab platform.
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evidence for plasticity in Magnetic nest building orientation in laboratory mice
Animal Behaviour, 2018Co-Authors: Michael S Painter, Madison Davis, Shruthi Ganesh, Ella Rak, Kelsie Brumet, Hunter Bayne, Pascal E Malkemper, John B PhillipsAbstract:Previous studies have shown that mammals exhibit two distinct forms of Magnetic behaviour: spontaneous Magnetic alignment and learned Magnetic Compass orientation. However, it remains to be determined whether the type of Magnetic response is species specific (i.e. species exhibit either learned Magnetic Compass responses or spontaneous Magnetic orientation). Alternatively, learned and spontaneous Magnetic orientation may be context dependent and expressed in the same species under different conditions, e.g. motivational, physiological and/or environmental. Using C57BL/6J laboratory mice, we provide evidence for multiple spatial responses to Magnetic cues in the same species. In a series of three similar nest-building experiments in which mice were trained to construct nests in one of four Magnetic directions, mice either positioned nests along a fixed northeast–southwest Magnetic axis (Series 1), independent of the trained direction, and similar to spontaneous Magnetic alignment responses in other vertebrates, or exhibited learned Magnetic Compass orientation in the direction away from (Series 2) or towards (Series 3) the sheltered end of the Magnetic axis they had been exposed to during the training period. Importantly, the responses elicited in each series paralleled changes in the experimental protocols and may help to explain the variation in Magnetic behaviours. Furthermore, the plasticity in the Magnetic orientation exhibited by laboratory mice suggests that Magnetic cues play important role in the spatial ecology of epigean rodents. Characterizing the factors that elicit these responses will shed light on the adaptive significance of spontaneous Magnetic alignment, a widespread but poorly understood spatial behaviour. In addition, future studies with similar nest-building assays will likely play a role in helping to determine whether Magnetic Compass orientation and spontaneous Magnetic alignment are mediated by the same underlying mechanisms of magnetoreception.
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DOI 10.1007/s00265-005-0951-5 ORIGINAL ARTICLE
2015Co-Authors: John B Phillips, J. B. PhillipsAbstract:Abstract Experiments were carried out to investigate the use of Magnetic Compass cues in the nocturnal homing ori-entation of the alpine newt Triturus alpestris. Tests were carried out at a site 9 km to the east–northeast of the breed-ing pond. Newts were tested at night in an outdoor circular arena that provided an unimpeded view of celestial cues, in one of four symmetrical alignments of an earth-strength Magnetic field. In tests carried out under partly cloudy skies newts exhibited homeward Magnetic Compass orientation. Because the moon was visible in some trials, but obscured by clouds in others, we investigated whether the presence of the moon contributed to the scatter in the distribution of Magnetic bearings. When the moon was visible, the distri-bution of Magnetic bearings was more scattered than when the moon was obscured by clouds, although in neither case was the distribution significant due, in part, to the small sample sizes. Moreover, when the moon was visible, newts oriented along a bimodal axis perpendicular to the moon azimuth, suggesting that the presence of the moon may have affected the newts behavior. To provide a more rigorous test of the role of Magnetic Compass cues when celestial cues were unavailable, nocturnal tests were carried out during the following migratory season under total overcast. In the absence of celestial Compass cues, the distribution of mag-netic bearings exhibited highly significant orientation in th
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Use of a light-dependent Magnetic Compass for y-axis orientation in European common frog (Rana temporaria) tadpoles
Journal of Comparative Physiology A, 2013Co-Authors: Francisco Javier Diego-rasilla, Rosa M Luengo, John B PhillipsAbstract:We provide evidence for the use of a Magnetic Compass for y -axis orientation (i.e., orientation along the shore-deep water axis) by tadpoles of the European common frog ( Rana temporaria ). Furthermore, our study provides evidence for a wavelength-dependent effect of light on Magnetic Compass orientation in amphibians. Tadpoles trained and then tested under full-spectrum light displayed Magnetic Compass orientation that coincided with the trained shore-deep water axes of their training tanks. Conversely, tadpoles trained under long-wavelength (≥500 nm) light and tested under full-spectrum light, and tadpoles trained under full-spectrum light and tested under long-wavelength (≥500 nm) light, exhibited a 90° shift in Magnetic Compass orientation relative to the trained y -axis direction. Our results are consistent with earlier studies showing that the observed 90° shift in the direction of Magnetic Compass orientation under long-wavelength (≥500 nm) light is due to a direct effect of light on the underlying magnetoreception mechanism. These findings also show that wavelength-dependent effects of light do not compromise the function of the Magnetic Compass under a wide range of natural lighting conditions, presumably due to a large asymmetry in the relatively sensitivity of antagonistic short- and long-wavelength inputs to the light-dependent Magnetic Compass.
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Magnetic Compass Orientation in the European Eel
PloS one, 2013Co-Authors: Caroline M. F. Durif, John B Phillips, Howard I. Browman, Anne Berit Skiftesvik, L. Asbjørn Vøllestad, Hans H. StockhausenAbstract:European eel migrate from freshwater or coastal habitats throughout Europe to their spawning grounds in the Sargasso Sea. However, their route (∼ 6000 km) and orientation mechanisms are unknown. Several attempts have been made to prove the existence of magnetoreception in Anguilla sp., but none of these studies have demonstrated Magnetic Compass orientation in earth-strength Magnetic field intensities. We tested eels in four altered Magnetic field conditions where Magnetic North was set at geographic North, South, East, or West. Eels oriented in a manner that was related to the tank in which they were housed before the test. At lower temperature (under 12°C), their orientation relative to Magnetic North corresponded to the direction of their displacement from the holding tank. At higher temperatures (12–17°C), eels showed bimodal orientation along an axis perpendicular to the axis of their displacement. These temperature-related shifts in orientation may be linked to the changes in behavior that occur between the warm season (during which eels are foraging) and the colder fall and winter (during which eels undertake their migrations). These observations support the conclusion that 1. eels have a Magnetic Compass, and 2. they use this sense to orient in a direction that they have registered moments before they are displaced. The adaptive advantage of having a Magnetic Compass and learning the direction in which they have been displaced becomes clear when set in the context of the eel’s seaward migration. For example, if their migration is halted or blocked, as it is the case when environmental conditions become unfavorable or when they encounter a barrier, eels would be able to resume their movements along their old bearing when conditions become favorable again or when they pass by the barrier.
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Light-dependent Magnetic Compass in Iberian green frog tadpoles
Naturwissenschaften, 2010Co-Authors: Francisco Javier Diego-rasilla, Rosa Milagros Luengo, John B PhillipsAbstract:Here, we provide evidence for a wavelength-dependent effect of light on Magnetic Compass orientation in Pelophylax perezi (order Anura), similar to that observed in Rana catesbeiana (order Anura) and Notophthalmus viridescens (order Urodela), and confirm for the first time in an anuran amphibian that a 90° shift in the direction of Magnetic Compass orientation under long-wavelength light (≥500 nm) is due to a direct effect of light on the underlying magnetoreception mechanism. Although Magnetic Compass orientation in other animals (e.g., birds and some insects) has been shown to be influenced by the wavelength and/or intensity of light, these two amphibian orders are the only taxa for which there is direct evidence that the Magnetic Compass is light-dependent. The remarkable similarities in the light-dependent Magnetic Compasses of anurans and urodeles, which have evolved as separate clades for at least 250 million years, suggest that the light-dependent magnetoreception mechanism is likely to have evolved in the common ancestor of the Lissamphibia (Early Permian, ~294 million years) and, possibly, much earlier. Also, we discuss a number of similarities between the functional properties of the light-dependent Magnetic Compass in amphibians and blue light-dependent responses to Magnetic stimuli in Drosophila melanogaster , which suggest that the wavelength-dependent 90° shift in amphibians may be due to light activation of different redox forms of a cryptochrome photopigment. Finally, we relate these findings to earlier studies showing that the pineal organ of newts is the site of the light-dependent Magnetic Compass and recent neurophysiological evidence showing Magnetic field sensitivity in the frog frontal organ (an outgrowth of the pineal).
P J Hore - One of the best experts on this subject based on the ideXlab platform.
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cryptochrome 1a localisation in light and dark adapted retinae of several migratory and non migratory bird species no signs of light dependent activation
Ethology Ecology & Evolution, 2021Co-Authors: Petra Bolte, Angelika Einwich, P J Hore, Dominik Heyers, Regina Feederle, Raisa Chetverikova, Pranav Kumar Seth, Irina Wojahn, Ulrike Janssenbienhold, Karin DedekAbstract:The Magnetic Compass of birds seems to be based on light-dependent radical-pair processes in the eyes. Cryptochromes are currently the only candidate proteins known in vertebrates that may serve as...
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Navigation of migratory songbirds: a quantum Magnetic Compass sensor
'Walter de Gruyter GmbH', 2021Co-Authors: Frederiksen A, P J Hore, Schuhmann F, Gruening G, Sy Wong, Hanic MAbstract:The remarkable ability of migratory birds to navigate accurately using the geoMagnetic field for journeys of thousands of kilometres is currently thought to arise from radical pair reactions inside a protein called cryptochrome. In this article, we explain the quantum mechanical basis of the radical pair mechanism and why it is currently the dominant theory of Compass magnetoreception. We also provide a brief account of two important computational simulation techniques that are used to study the mechanism in cryptochrome: spin dynamics and molecular dynamics. At the end we provide an overview of current research on quantum mechanical processes in avian cryptochromes and the computational models for describing them
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Chiral-induced spin selectivity in the formation and recombination of radical pairs: cryptochrome magnetoreception and EPR detection
'IOP Publishing', 2021Co-Authors: P J Hore, Luo JAbstract:That the rates and yields of reactions of organic radicals can be spin dependent is well known in the context of the radical pair mechanism (RPM). Less well known, but still well established, is the chiral-induced spin selectivity (CISS) effect in which chiral molecules act as spin filters that preferentially transmit electrons with spins polarized parallel or antiparallel to their direction of motion. Starting from the assumption that CISS can arise in electron transfer reactions of radical pairs, we propose a simple way to include CISS in conventional models of radical pair spin dynamics. We show that CISS can (a) increase the sensitivity of radical pairs to the direction of a weak external Magnetic field, (b) change the dependence of the Magnetic field effect on the reaction rate constants, and (c) destroy the field-inversion symmetry characteristic of the RPM. We argue that CISS polarization effects could be observable by EPR (electron paraMagnetic resonance) of oriented samples either as differences in continuous wave, time-resolved spectra recorded with the spectrometer field parallel or perpendicular to the CISS quantization axis or as signals in the in-phase channel of an out-of-phase ESEEM (electron spin echo envelope modulation) experiment. Finally we assess whether CISS might be relevant to the hypothesis that the Magnetic Compass of migratory songbirds relies on photochemically-formed radical pairs in cryptochrome flavoproteins. Although CISS effects offer the possibility of evolving a more sensitive or precise Compass, the associated lack of field-inversion symmetry has not hitherto been observed in behavioural experiments. In addition, it may no longer be safe to assume that the observation of a polar Magnetic Compass response in an animal can be used as evidence against a radical pair sensory mechanism
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Angular precision of radical pair Compass magnetoreceptors
'Elsevier BV', 2021Co-Authors: Ren Y, Hg Hiscock, P J HoreAbstract:The light-dependent Magnetic Compass sense of night-migratory songbirds is thought to rely on Magnetically sensitive chemical reactions of radical pairs in cryptochrome proteins located in the birds’ eyes. Recently, an information theory approach was developed that provides a strict lower bound on the precision with which a bird could estimate its head direction using only geoMagnetic cues and a cryptochrome-based radical pair sensor. By means of this lower bound, we show here how the performance of the Compass sense could be optimized by adjusting the orientation of cryptochrome molecules within photoreceptor cells, the distribution of cells around the retina, and the effects of the geoMagnetic field on the photochemistry of the radical pair
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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
Journal of the Royal Society Interface, 2019Co-Authors: Dmitry Kobylkov, P J Hore, Hamish G Hiscock, Joe Wynn, Michael Winklhofer, Raisa Chetverikova, Henrik MouritsenAbstract: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.
Roswitha Wiltschko - One of the best experts on this subject based on the ideXlab platform.
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Report Magnetoreception of Directional Information in Birds Requires Nondegraded Vision
2020Co-Authors: Katrin Stapput, Roswitha Wiltschko, Onur Gü Ntü Rkü, Klaus-peter Hoffmann, Wolfgang WiltschkoAbstract:Summary The Magnetic Compass orientation of birds is light dependen
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Lateralization of the Avian Magnetic Compass: Analysis of Its Early Plasticity
MDPI AG, 2017Co-Authors: Dennis Gehring, Wolfgang Wiltschko, Onur Gunturkun, Roswitha WiltschkoAbstract:In European Robins, Erithacus rubecula, the Magnetic Compass is lateralized in favor of the right eye/left hemisphere of the brain. This lateralization develops during the first winter and initially shows a great plasticity. During the first spring migration, it can be temporarily removed by covering the right eye. In the present paper, we used the migratory orientation of robins to analyze the circumstances under which the lateralization can be undone. Already a period of 1½ h being monocularly left-eyed before tests began proved sufficient to restore the ability to use the left eye for orientation, but this effect was rather short-lived, as lateralization recurred again within the next 1½ h. Interpretable Magnetic information mediated by the left eye was necessary for removing the lateralization. In addition, monocularly, the left eye seeing robins could adjust to Magnetic intensities outside the normal functional window, but this ability was not transferred to the “right-eye system”. Our results make it clear that asymmetry of Magnetic Compass perception is amenable to short-term changes, depending on lateralized stimulation. This could mean that the left hemispheric dominance for the analysis of Magnetic Compass information depends on lateralized interhemispheric interactions that in young birds can swiftly be altered by environmental effects
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seasonally changing cryptochrome 1b expression in the retinal ganglion cells of a migrating passerine bird
PLOS ONE, 2016Co-Authors: Christine Niesner, Susanne Denzau, Leo Peichl, Julia Christina Gross, Gerta Fleissner, Wolfgang Wiltschko, Roswitha WiltschkoAbstract:Cryptochromes, blue-light absorbing proteins involved in the circadian clock, have been proposed to be the receptor molecules of the avian Magnetic Compass. In birds, several cryptochromes occur: Cryptochrome 2, Cryptochrome 4 and two splice products of Cryptochrome 1, Cry1a and Cry1b. With an antibody not distinguishing between the two splice products, Cryptochrome 1 had been detected in the retinal ganglion cells of garden warblers during migration. A recent study located Cry1a in the outer segments of UV/V-cones in the retina of domestic chickens and European robins, another migratory species. Here we report the presence of cryptochrome 1b (eCry1b) in retinal ganglion cells and displaced ganglion cells of European Robins, Erithacus rubecula. Immuno-histochemistry at the light microscopic and electron microscopic level showed eCry1b in the cell plasma, free in the cytosol as well as bound to membranes. This is supported by immuno-blotting. However, this applies only to robins in the migratory state. After the end of the migratory phase, the amount of eCry1b was markedly reduced and hardly detectable. In robins, the amount of eCry1b in the retinal ganglion cells varies with season: it appears to be strongly expressed only during the migratory period when the birds show nocturnal migratory restlessness. Since the avian Magnetic Compass does not seem to be restricted to the migratory phase, this seasonal variation makes a role of eCry1b in magnetoreception rather unlikely. Rather, it could be involved in physiological processes controlling migratory restlessness and thus enabling birds to perform their nocturnal flights.
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Magnetic orientation of migratory robins erithacus rubecula under long wavelength light
The Journal of Experimental Biology, 2011Co-Authors: Roswitha Wiltschko, Susanne Denzau, Peter Thalau, Dennis Gehring, Wolfgang WiltschkoAbstract:The avian Magnetic Compass is an inclination Compass that appears to be based on radical pair processes. It requires light from the short-wavelength range of the spectrum up to 565 nm green light; under longer wavelengths, birds are disoriented. When pre-exposed to longer wavelengths for 1 h, however, they show oriented behavior. This orientation is analyzed under 582 nm yellow light and 645 nm red light in the present study: while the birds in spring prefer northerly directions, they do not show southerly tendencies in autumn. Inversion of the vertical component does not have an effect whereas reversal of the horizontal component leads to a corresponding shift, indicating that a polar response to the Magnetic field is involved. Oscillating Magnetic fields in the MHz range do not affect the behavior but anesthesia of the upper beak causes disorientation. This indicates that the Magnetic information is no longer provided by the radical pair mechanism in the eye but by the magnetite-based receptors in the skin of the beak. Exposure to long-wavelength light thus does not expand the spectral range in which the Magnetic Compass operates but instead causes a different mechanism to take over and control orientation.
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migratory orientation Magnetic Compass orientation of garden warblers sylvia borin after a simulated crossing of the Magnetic equator
Ethology, 2010Co-Authors: Wolfgang Wiltschko, Roswitha WiltschkoAbstract:Since the birds' Magnetic Compass works as an inclination Compass using the axial course of the Magnetic field lines and their inclination, transequatorial migrants have to reverse their reaction with respect to the Magnetic field after crossing the Magnetic equator. Garden Warblers, long distance migrants breeding in Europe and wintering in tropical and southern Africa, were tested during autumn in the local geoMagnetic field on the northern hemisphere. The experimental group was exposed to a field with horizontal field lines, simulating equator crossing, at the beginning of October; afterwards the birds were tested in the local geoMagnetic field again. While the controls showed southerly tendencies during the entire season, the experimentals reversed their directional tendencies after staying in the horizontal field and now preferred northerly directions. In a field of the southern hemisphere, this preference corresponds to a southern course which would have meant the continuation of their migration flight.
Wolfgang Wiltschko - One of the best experts on this subject based on the ideXlab platform.
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Report Magnetoreception of Directional Information in Birds Requires Nondegraded Vision
2020Co-Authors: Katrin Stapput, Roswitha Wiltschko, Onur Gü Ntü Rkü, Klaus-peter Hoffmann, Wolfgang WiltschkoAbstract:Summary The Magnetic Compass orientation of birds is light dependen
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Lateralization of the Avian Magnetic Compass: Analysis of Its Early Plasticity
MDPI AG, 2017Co-Authors: Dennis Gehring, Wolfgang Wiltschko, Onur Gunturkun, Roswitha WiltschkoAbstract:In European Robins, Erithacus rubecula, the Magnetic Compass is lateralized in favor of the right eye/left hemisphere of the brain. This lateralization develops during the first winter and initially shows a great plasticity. During the first spring migration, it can be temporarily removed by covering the right eye. In the present paper, we used the migratory orientation of robins to analyze the circumstances under which the lateralization can be undone. Already a period of 1½ h being monocularly left-eyed before tests began proved sufficient to restore the ability to use the left eye for orientation, but this effect was rather short-lived, as lateralization recurred again within the next 1½ h. Interpretable Magnetic information mediated by the left eye was necessary for removing the lateralization. In addition, monocularly, the left eye seeing robins could adjust to Magnetic intensities outside the normal functional window, but this ability was not transferred to the “right-eye system”. Our results make it clear that asymmetry of Magnetic Compass perception is amenable to short-term changes, depending on lateralized stimulation. This could mean that the left hemispheric dominance for the analysis of Magnetic Compass information depends on lateralized interhemispheric interactions that in young birds can swiftly be altered by environmental effects
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seasonally changing cryptochrome 1b expression in the retinal ganglion cells of a migrating passerine bird
PLOS ONE, 2016Co-Authors: Christine Niesner, Susanne Denzau, Leo Peichl, Julia Christina Gross, Gerta Fleissner, Wolfgang Wiltschko, Roswitha WiltschkoAbstract:Cryptochromes, blue-light absorbing proteins involved in the circadian clock, have been proposed to be the receptor molecules of the avian Magnetic Compass. In birds, several cryptochromes occur: Cryptochrome 2, Cryptochrome 4 and two splice products of Cryptochrome 1, Cry1a and Cry1b. With an antibody not distinguishing between the two splice products, Cryptochrome 1 had been detected in the retinal ganglion cells of garden warblers during migration. A recent study located Cry1a in the outer segments of UV/V-cones in the retina of domestic chickens and European robins, another migratory species. Here we report the presence of cryptochrome 1b (eCry1b) in retinal ganglion cells and displaced ganglion cells of European Robins, Erithacus rubecula. Immuno-histochemistry at the light microscopic and electron microscopic level showed eCry1b in the cell plasma, free in the cytosol as well as bound to membranes. This is supported by immuno-blotting. However, this applies only to robins in the migratory state. After the end of the migratory phase, the amount of eCry1b was markedly reduced and hardly detectable. In robins, the amount of eCry1b in the retinal ganglion cells varies with season: it appears to be strongly expressed only during the migratory period when the birds show nocturnal migratory restlessness. Since the avian Magnetic Compass does not seem to be restricted to the migratory phase, this seasonal variation makes a role of eCry1b in magnetoreception rather unlikely. Rather, it could be involved in physiological processes controlling migratory restlessness and thus enabling birds to perform their nocturnal flights.
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Magnetic orientation of migratory robins erithacus rubecula under long wavelength light
The Journal of Experimental Biology, 2011Co-Authors: Roswitha Wiltschko, Susanne Denzau, Peter Thalau, Dennis Gehring, Wolfgang WiltschkoAbstract:The avian Magnetic Compass is an inclination Compass that appears to be based on radical pair processes. It requires light from the short-wavelength range of the spectrum up to 565 nm green light; under longer wavelengths, birds are disoriented. When pre-exposed to longer wavelengths for 1 h, however, they show oriented behavior. This orientation is analyzed under 582 nm yellow light and 645 nm red light in the present study: while the birds in spring prefer northerly directions, they do not show southerly tendencies in autumn. Inversion of the vertical component does not have an effect whereas reversal of the horizontal component leads to a corresponding shift, indicating that a polar response to the Magnetic field is involved. Oscillating Magnetic fields in the MHz range do not affect the behavior but anesthesia of the upper beak causes disorientation. This indicates that the Magnetic information is no longer provided by the radical pair mechanism in the eye but by the magnetite-based receptors in the skin of the beak. Exposure to long-wavelength light thus does not expand the spectral range in which the Magnetic Compass operates but instead causes a different mechanism to take over and control orientation.
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migratory orientation Magnetic Compass orientation of garden warblers sylvia borin after a simulated crossing of the Magnetic equator
Ethology, 2010Co-Authors: Wolfgang Wiltschko, Roswitha WiltschkoAbstract:Since the birds' Magnetic Compass works as an inclination Compass using the axial course of the Magnetic field lines and their inclination, transequatorial migrants have to reverse their reaction with respect to the Magnetic field after crossing the Magnetic equator. Garden Warblers, long distance migrants breeding in Europe and wintering in tropical and southern Africa, were tested during autumn in the local geoMagnetic field on the northern hemisphere. The experimental group was exposed to a field with horizontal field lines, simulating equator crossing, at the beginning of October; afterwards the birds were tested in the local geoMagnetic field again. While the controls showed southerly tendencies during the entire season, the experimentals reversed their directional tendencies after staying in the horizontal field and now preferred northerly directions. In a field of the southern hemisphere, this preference corresponds to a southern course which would have meant the continuation of their migration flight.
Henrik Mouritsen - One of the best experts on this subject based on the ideXlab platform.
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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
Journal of the Royal Society Interface, 2019Co-Authors: Dmitry Kobylkov, P J Hore, Hamish G Hiscock, Joe Wynn, Michael Winklhofer, Raisa Chetverikova, Henrik MouritsenAbstract: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.
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double cone localization and seasonal expression pattern suggest a role in magnetoreception for european robin cryptochrome 4
Current Biology, 2018Co-Authors: Anja Gunther, Petra Bolte, Angelika Einwich, Emil Sjulstok, Regina Feederle, Karlwilhelm Koch, Ilia A Solovyov, Henrik MouritsenAbstract:Summary Birds seem to use a light-dependent, radical-pair-based Magnetic Compass. In vertebrates, cryptochromes are the only class of proteins that form radical pairs upon photo-excitation. Therefore, they are currently the only candidate proteins for light-dependent magnetoreception. Cryptochrome 4 (Cry4) is particularly interesting because it has only been found in vertebrates that use a Magnetic Compass. However, its structure and localization within the retina has remained unknown. Here, we sequenced night-migratory European robin ( Erithacus rubecula ) Cry4 from the retina and predicted the currently unresolved structure of the erCry4 protein, which suggests that erCry4 should bind Flavin. We also found that Cry1a , Cry1b , and Cry2 mRNA display robust circadian oscillation patterns, whereas Cry4 shows only a weak circadian oscillation. When we compared the relative mRNA expression levels of the cryptochromes during the spring and autumn migratory seasons relative to the non-migratory seasons in European robins and domestic chickens ( Gallus gallus ), the Cry4 mRNA expression level in European robin retinae, but not in chicken retinae, is significantly higher during the migratory season compared to the non-migratory seasons. Cry4 protein is specifically expressed in the outer segments of the double cones and long-wavelength single cones in European robins and chickens. A localization of Cry4 in double cones seems to be ideal for light-dependent magnetoreception. Considering all of the data presented here, especially including its localization within the European robin retina, its likely binding of Flavin, and its increased expression during the migratory season in the migratory bird but not in chicken, Cry4 could be the magnetoreceptive protein.
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disruption of Magnetic Compass orientation in migratory birds by radiofrequency electroMagnetic fields
Biophysical Journal, 2017Co-Authors: Hamish G Hiscock, Henrik Mouritsen, David E Manolopoulos, P J HoreAbstract:The radical-pair mechanism has been put forward as the basis of the Magnetic Compass sense of migratory birds. Some of the strongest supporting evidence has come from behavioral experiments in which birds exposed to weak time-dependent Magnetic fields lose their ability to orient in the geoMagnetic field. However, conflicting results and skepticism about the requirement for abnormally long quantum coherence lifetimes have cast a shroud of uncertainty over these potentially pivotal studies. Using a recently developed computational approach, we explore the effects of various radiofrequency Magnetic fields on biologically plausible radicals within the theoretical framework of radical-pair magnetoreception. We conclude that the current model of radical-pair magnetoreception is unable to explain the findings of the reported behavioral experiments. Assuming that an unknown mechanism amplifies the predicted effects, we suggest experimental conditions that have the potential to distinguish convincingly between the two distinct families of radical pairs currently postulated as Magnetic Compass sensors. We end by making recommendations for experimental protocols that we hope will increase the chance that future experiments can be independently replicated.
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migratory blackcaps can use their Magnetic Compass at 5 degrees inclination but are completely random at 0 degrees inclination
Scientific Reports, 2016Co-Authors: Susanne Schwarze, Nilslasse Schneider, Nele Lefeldt, David Dreyer, Friederike Steenken, Nadine Thiele, Dmitry Kobylkov, Henrik MouritsenAbstract:It is known that night-migratory songbirds use a Magnetic Compass measuring the Magnetic inclination angle, i.e. the angle between the Earth's surface and the Magnetic field lines, but how do such birds orient at the Magnetic equator? A previous study reported that birds are completely randomly oriented in a horizontal north-south Magnetic field with 0° inclination angle. This seems counter-intuitive, because birds using an inclination Compass should be able to separate the north-south axis from the east-west axis, so that bimodal orientation might be expected in a horizontal field. Furthermore, little is known about how shallow inclination angles migratory birds can still use for orientation. In this study, we tested the Magnetic Compass orientation of night-migratory Eurasian blackcaps (Sylvia atricapilla) in Magnetic fields with 5° and 0° inclination. At 5° inclination, the birds oriented as well as they did in the normal 67° inclined field in Oldenburg. In contrast, they were completely randomly oriented in the horizontal field, showing no sign of bimodality. Our results indicate that the inclination limit for the Magnetic Compass of the blackcap is below 5° and that these birds indeed seem completely unable to use their Magnetic Compass for orientation in a horizontal Magnetic field.
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the quantum needle of the avian Magnetic Compass
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Hamish G Hiscock, Henrik Mouritsen, David E Manolopoulos, Susannah Bourne Worster, Daniel R Kattnig, Charlotte Steers, Ye Jin, P J HoreAbstract:Migratory birds have a light-dependent Magnetic Compass, the mechanism of which is thought to involve radical pairs formed photochemically in cryptochrome proteins in the retina. Theoretical descriptions of this Compass have thus far been unable to account for the high precision with which birds are able to detect the direction of the Earth's Magnetic field. Here we use coherent spin dynamics simulations to explore the behavior of realistic models of cryptochrome-based radical pairs. We show that when the spin coherence persists for longer than a few microseconds, the output of the sensor contains a sharp feature, referred to as a spike. The spike arises from avoided crossings of the quantum mechanical spin energy-levels of radicals formed in cryptochromes. Such a feature could deliver a heading precision sufficient to explain the navigational behavior of migratory birds in the wild. Our results (i) afford new insights into radical pair magnetoreception, (ii) suggest ways in which the performance of the Compass could have been optimized by evolution, (iii) may provide the beginnings of an explanation for the Magnetic disorientation of migratory birds exposed to anthropogenic electroMagnetic noise, and (iv) suggest that radical pair magnetoreception may be more of a quantum biology phenomenon than previously realized.
