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Putman NF. Magnetosensation. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2022; 208:1-7. [PMID: 35098367 DOI: 10.1007/s00359-021-01538-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 12/17/2021] [Accepted: 12/20/2021] [Indexed: 10/19/2022]
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2
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Engels S, Treiber CD, Salzer MC, Michalik A, Ushakova L, Keays DA, Mouritsen H, Heyers D. Lidocaine is a nocebo treatment for trigeminally mediated magnetic orientation in birds. J R Soc Interface 2018; 15:20180124. [PMID: 30089685 PMCID: PMC6127160 DOI: 10.1098/rsif.2018.0124] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Accepted: 07/13/2018] [Indexed: 12/30/2022] Open
Abstract
Even though previously described iron-containing structures in the upper beak of pigeons were almost certainly macrophages, not magnetosensitive neurons, behavioural and neurobiological evidence still supports the involvement of the ophthalmic branch of the trigeminal nerve (V1) in magnetoreception. In previous behavioural studies, inactivation of putative V1-associated magnetoreceptors involved either application of the surface anaesthetic lidocaine to the upper beak or sectioning of V1. Here, we compared the effects of lidocaine treatment, V1 ablations and sham ablations on magnetic field-driven neuronal activation in V1-recipient brain regions in European robins. V1 sectioning led to significantly fewer Egr-1-expressing neurons in the trigeminal brainstem than in the sham-ablated birds, whereas lidocaine treatment had no effect on neuronal activation. Furthermore, Prussian blue staining showed that nearly all iron-containing cells in the subepidermal layer of the upper beak are nucleated and are thus not part of the trigeminal nerve, and iron-containing cells appeared in highly variable numbers at inconsistent locations between individual robins and showed no systematic colocalization with a neuronal marker. Our data suggest that lidocaine treatment has been a nocebo to the birds and a placebo for the experimenters. Currently, the nature and location of any V1-associated magnetosensor remains elusive.
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Affiliation(s)
- Svenja Engels
- AG Neurosensorics, University of Oldenburg, Oldenburg, Germany
- Research Centre for Neurosensory Sciences, University of Oldenburg, Oldenburg, Germany
| | | | | | - Andreas Michalik
- AG Neurosensorics, University of Oldenburg, Oldenburg, Germany
- Research Centre for Neurosensory Sciences, University of Oldenburg, Oldenburg, Germany
| | | | | | - Henrik Mouritsen
- AG Neurosensorics, University of Oldenburg, Oldenburg, Germany
- Research Centre for Neurosensory Sciences, University of Oldenburg, Oldenburg, Germany
| | - Dominik Heyers
- AG Neurosensorics, University of Oldenburg, Oldenburg, Germany
- Research Centre for Neurosensory Sciences, University of Oldenburg, Oldenburg, Germany
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Abstract
Diverse animals ranging from worms and insects to birds and turtles perform impressive journeys using the magnetic field of the earth as a cue. Although major cellular and molecular mechanisms for sensing mechanical and chemical cues have been elucidated over the past three decades, the mechanisms that animals use to sense magnetic fields remain largely mysterious. Here we survey progress on the search for magnetosensory neurons and magnetosensitive molecules important for animal behaviors. Emphasis is placed on magnetosensation in insects and birds, as well as on the magnetosensitive neuron pair AFD in the nematode Caenorhabditis elegans. We also review conventional criteria used to define animal magnetoreceptors and suggest how approaches used to identify receptors for other sensory modalities may be adapted for magnetoreceptors. Finally, we discuss prospects for underutilized and novel approaches to identify the elusive magnetoreceptors in animals.
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Affiliation(s)
- Benjamin L Clites
- Institute for Cell and Molecular Biology, Center for Brain, Behavior and Evolution, Center for Learning and Memory, Waggoner Center for Alcohol and Addiction Research, and Department of Neuroscience, University of Texas, Austin, Texas 78712; ,
| | - Jonathan T Pierce
- Institute for Cell and Molecular Biology, Center for Brain, Behavior and Evolution, Center for Learning and Memory, Waggoner Center for Alcohol and Addiction Research, and Department of Neuroscience, University of Texas, Austin, Texas 78712; ,
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Nießner C, Winklhofer M. Radical-pair-based magnetoreception in birds: radio-frequency experiments and the role of cryptochrome. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2017; 203:499-507. [PMID: 28612234 PMCID: PMC5522499 DOI: 10.1007/s00359-017-1189-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 05/28/2017] [Accepted: 05/29/2017] [Indexed: 11/30/2022]
Abstract
The radical-pair hypothesis of magnetoreception has gained a lot of momentum, since the flavoprotein cryptochrome was postulated as a structural candidate to host magnetically sensitive chemical reactions. Here, we first discuss behavioral tests using radio-frequency magnetic fields (0.1-10 MHz) to specifically disturb a radical-pair-based avian magnetic compass sense. While disorienting effects of broadband RF magnetic fields have been replicated independently in two competing labs, the effects of monochromatic RF magnetic fields administered at the electronic Larmor frequency (~1.3 MHz) are disparate. We give technical recommendations for future RF experiments. We then focus on two candidate magnetoreceptor proteins in birds, Cry1a and Cry1b, two splice variants of the same gene (Cry1). Immunohistochemical studies have identified Cry1a in the outer segments of the ultraviolet/violet-sensitive cone photoreceptors and Cry1b in the cytosol of retinal ganglion cells. The identification of the host neurons of these cryptochromes and their subcellular expression patterns presents an important advance, but much work lies ahead to gain some functional understanding. In particular, interaction partners of cryptochrome Cry1a and Cry1b remain to be identified. A candidate partner for Cry4 was previously suggested, but awaits independent replication.
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Affiliation(s)
- Christine Nießner
- Ernst Strüngmann Institute for Neuroscience, Deutschordenstr 46, 60528, Frankfurt am Main, Germany
| | - Michael Winklhofer
- Institute for Biology and Environmental Sciences IBU, School of Mathematics and Science, University of Oldenburg, 26111, Oldenburg, Germany.
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Lateralization of the Avian Magnetic Compass: Analysis of Its Early Plasticity. Symmetry (Basel) 2017. [DOI: 10.3390/sym9050077] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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6
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The importance of illumination in nest site choice and nest characteristics of cavity nesting birds. Sci Rep 2017; 7:1329. [PMID: 28465542 PMCID: PMC5430998 DOI: 10.1038/s41598-017-01430-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 03/28/2017] [Indexed: 11/09/2022] Open
Abstract
Light has a significant impact on many aspects of avian biology, physiology and behaviour. An increasing number of studies show that illumination may positively influences birds' offspring fitness by e.g. acceleration of embryo development, stimulation of skeleton growth or regulation of circadian rhythm. Because nest cavities have especially low illumination, suitable light levels may be especially important for species which nest there. We may therefore expect that birds breeding in relatively dim conditions should prefer brighter nest sites and/or evolve behavioral mechanisms to secure sufficient light levels in the nest. Using nest boxes with modified internal illumination, we experimentally tested whether light regime is a cue for nest site selection of secondary cavity-nesting species. Additionally, we investigated whether nest building strategies are tuned to internal illumination. Our results demonstrate that, nest boxes with elevated illumination were chosen twice as often as dark nest boxes. Moreover, birds built higher nests in dark nest boxes than birds in boxes with elevated illumination, which suggests a mechanism of compensating for low light conditions. Our results provide the first experimental support for the idea that nest site choice and nest building behaviour in cavity-nesting birds are influenced by ambient illumination.
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Polarized light modulates light-dependent magnetic compass orientation in birds. Proc Natl Acad Sci U S A 2016; 113:1654-9. [PMID: 26811473 DOI: 10.1073/pnas.1513391113] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
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.
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Lefeldt N, Heyers D, Schneider NL, Engels S, Elbers D, Mouritsen H. Magnetic field-driven induction of ZENK in the trigeminal system of pigeons (Columba livia). J R Soc Interface 2015; 11:20140777. [PMID: 25232052 DOI: 10.1098/rsif.2014.0777] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Magnetoreception remains one of the few unsolved mysteries in sensory biology. The upper beak, which is innervated by the ophthalmic branch of the trigeminal nerve (V1), has been suggested to contain magnetic sensors based on ferromagnetic structures. Recently, its existence in pigeons has been seriously challenged by studies suggesting that the previously described iron-accumulations are macrophages, not magnetosensitive nerve endings. This raised the fundamental question of whether V1 is involved in magnetoreception in pigeons at all. We exposed pigeons to either a constantly changing magnetic field (CMF), to a zero magnetic field providing no magnetic information, or to CMF conditions after V1 was cut bilaterally. Using immediate early genes as a marker of neuronal responsiveness, we report that the trigeminal brainstem nuclei of pigeons, which receive V1 input, are activated under CMF conditions and that this neuronal activation disappears if the magnetic stimuli are removed or if V1 is cut. Our data suggest that the trigeminal system in pigeons is involved in processing magnetic field information and that V1 transmits this information from currently unknown, V1-associated magnetosensors to the brain.
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Affiliation(s)
- Nele Lefeldt
- AG Neurosensorik/Animal Navigation, Institute of Biological and Environmental Sciences, University Oldenburg, 26111 Oldenburg, Germany
| | - Dominik Heyers
- AG Neurosensorik/Animal Navigation, Institute of Biological and Environmental Sciences, University Oldenburg, 26111 Oldenburg, Germany
| | - Nils-Lasse Schneider
- AG Neurosensorik/Animal Navigation, Institute of Biological and Environmental Sciences, University Oldenburg, 26111 Oldenburg, Germany
| | - Svenja Engels
- AG Neurosensorik/Animal Navigation, Institute of Biological and Environmental Sciences, University Oldenburg, 26111 Oldenburg, Germany
| | - Dana Elbers
- AG Neurosensorik/Animal Navigation, Institute of Biological and Environmental Sciences, University Oldenburg, 26111 Oldenburg, Germany
| | - Henrik Mouritsen
- AG Neurosensorik/Animal Navigation, Institute of Biological and Environmental Sciences, University Oldenburg, 26111 Oldenburg, Germany
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Wiltschko R, Munro U, Ford H, Stapput K, Thalau P, Wiltschko W. Orientation of migratory birds under ultraviolet light. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2014; 200:399-407. [PMID: 24718656 DOI: 10.1007/s00359-014-0898-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Revised: 03/05/2014] [Accepted: 03/07/2014] [Indexed: 11/25/2022]
Abstract
In view of the finding that cryptochrome 1a, the putative receptor molecule for the avian magnetic compass, is restricted to the ultraviolet single cones in European Robins, we studied the orientation behaviour of robins and Australian Silvereyes under monochromatic ultraviolet (UV) light. At low intensity UV light of 0.3 mW/m(2), birds showed normal migratory orientation by their inclination compass, with the directional information originating in radical pair processes in the eye. At 2.8 mW/m(2), robins showed an axial preference in the east-west axis, whereas silvereyes preferred an easterly direction. At 5.7 mW/m(2), robins changed direction to a north-south axis. When UV light was combined with yellow light, robins showed easterly 'fixed direction' responses, which changed to disorientation when their upper beak was locally anaesthetised with xylocaine, indicating that they were controlled by the magnetite-based receptors in the beak. Orientation under UV light thus appears to be similar to that observed under blue, turquoise and green light, albeit the UV responses occur at lower light levels, probably because of the greater light sensitivity of the UV cones. The orientation under UV light and green light suggests that at least at the level of the retina, magnetoreception and vision are largely independent of each other.
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Affiliation(s)
- Roswitha Wiltschko
- Fachbereich Biowissenschaften der, J.W.Goethe-Universität Frankfurt, Max von Laue Straße 13, 60438, Frankfurt am Main, Germany,
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10
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Cassone VM. Avian circadian organization: a chorus of clocks. Front Neuroendocrinol 2014; 35:76-88. [PMID: 24157655 PMCID: PMC3946898 DOI: 10.1016/j.yfrne.2013.10.002] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 07/18/2013] [Accepted: 10/09/2013] [Indexed: 12/24/2022]
Abstract
In birds, biological clock function pervades all aspects of biology, controlling daily changes in sleep: wake, visual function, song, migratory patterns and orientation, as well as seasonal patterns of reproduction, song and migration. The molecular bases for circadian clocks are highly conserved, and it is likely the avian molecular mechanisms are similar to those expressed in mammals, including humans. The central pacemakers in the avian pineal gland, retinae and SCN dynamically interact to maintain stable phase relationships and then influence downstream rhythms through entrainment of peripheral oscillators in the brain controlling behavior and peripheral tissues. Birds represent an excellent model for the role played by biological clocks in human neurobiology; unlike most rodent models, they are diurnal, they exhibit cognitively complex social interactions, and their circadian clocks are more sensitive to the hormone melatonin than are those of nocturnal rodents.
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Affiliation(s)
- Vincent M Cassone
- Department of Biology, University of Kentucky, Lexington, KY 40506, United States.
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11
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De Groof G, Jonckers E, Güntürkün O, Denolf P, Van Auderkerke J, Van der Linden A. Functional MRI and functional connectivity of the visual system of awake pigeons. Behav Brain Res 2013; 239:43-50. [PMID: 23137696 DOI: 10.1016/j.bbr.2012.10.044] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 10/23/2012] [Accepted: 10/29/2012] [Indexed: 02/02/2023]
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12
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Ocklenburg S, Ströckens F, Güntürkün O. Lateralisation of conspecific vocalisation in non-human vertebrates. Laterality 2013; 18:1-31. [DOI: 10.1080/1357650x.2011.626561] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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13
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Gehring D, Wiltschko W, Güntürkün O, Denzau S, Wiltschko R. Development of lateralization of the magnetic compass in a migratory bird. Proc Biol Sci 2012; 279:4230-5. [PMID: 22933375 PMCID: PMC3441093 DOI: 10.1098/rspb.2012.1654] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The magnetic compass of a migratory bird, the European robin (Erithacus rubecula), was shown to be lateralized in favour of the right eye/left brain hemisphere. However, this seems to be a property of the avian magnetic compass that is not present from the beginning, but develops only as the birds grow older. During first migration in autumn, juvenile robins can orient by their magnetic compass with their right as well as with their left eye. In the following spring, however, the magnetic compass is already lateralized, but this lateralization is still flexible: it could be removed by covering the right eye for 6 h. During the following autumn migration, the lateralization becomes more strongly fixed, with a 6 h occlusion of the right eye no longer having an effect. This change from a bilateral to a lateralized magnetic compass appears to be a maturation process, the first such case known so far in birds. Because both eyes mediate identical information about the geomagnetic field, brain asymmetry for the magnetic compass could increase efficiency by setting the other hemisphere free for other processes.
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Affiliation(s)
- Dennis Gehring
- FB Biowissenschaften, J.W. Goethe-Universität Frankfurt, Siesmayerstr. 70, 60054 Frankfurt am Main, Germany
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Bischof HJ, Nießner C, Peichl L, Wiltschko R, Wiltschko W. Avian ultraviolet/violet cones as magnetoreceptors: The problem of separating visual and magnetic information. Commun Integr Biol 2012; 4:713-6. [PMID: 22446535 DOI: 10.4161/cib.17338] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
In a recent paper, we described the localization of cryptochrome 1a in the retina of domestic chickens, Gallus gallus, and European robins, Erithacus rubecula: Cryptochrome 1a was found exclusively along the membranes of the disks in the outer segments of the ultraviolet/violet single cones. Cryptochrome has been suggested to act as receptor molecule for the avian magnetic compass, which would mean that the UV/V cones have a double function: they mediate vision in the short-wavelength range and, at the same time, magnetic directional information. This has important implications and raises a number of questions, in particular, how the two types of input are separated. Here, we point out several possibilities how this could be achieved.
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Mouritsen H, Hore PJ. The magnetic retina: light-dependent and trigeminal magnetoreception in migratory birds. Curr Opin Neurobiol 2012; 22:343-52. [DOI: 10.1016/j.conb.2012.01.005] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Revised: 01/03/2012] [Accepted: 01/17/2012] [Indexed: 10/28/2022]
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Solov'yov IA, Schulten K. Reaction kinetics and mechanism of magnetic field effects in cryptochrome. J Phys Chem B 2012; 116:1089-99. [PMID: 22171949 PMCID: PMC3266978 DOI: 10.1021/jp209508y] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Creatures as varied as mammals, fish, insects, reptiles, and birds have an intriguing sixth sense that allows them to orient themselves in the Earth's magnetic field. Despite decades of study, the physical basis of this magnetic sense remains elusive. A likely mechanism is furnished by magnetically sensitive radical pair reactions occurring in the retina, the light-sensitive part of animal eyes. A photoreceptor, cryptochrome, has been suggested to endow birds with magnetoreceptive abilities as the protein has been shown to exhibit the biophysical properties required for an animal magnetoreceptor to operate properly. Here, we propose a theoretical analysis method for identifying cryptochrome's signaling reactions involving comparison of measured and calculated reaction kinetics in cryptochrome. Application of the method yields an exemplary light-driven reaction cycle, supported through transient absorption and electron-spin-resonance observations together with known facts on avian magnetoreception. The reaction cycle permits one to predict magnetic field effects on cryptochrome activation and deactivation. The suggested analysis method gives insight into structural and dynamic design features required for optimal detection of the geomagnetic field by cryptochrome and suggests further experimental and theoretical studies.
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Oliveriusová L, Němec P, Králová Z, Sedláček F. Magnetic compass orientation in two strictly subterranean rodents: learned or species-specific innate directional preference? J Exp Biol 2012; 215:3649-54. [DOI: 10.1242/jeb.069625] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Summary
Evidence for magnetoreception in mammals remains limited. Magnetic compass orientation or magnetic alignment has been conclusively demonstrated in only a handful of mammalian species. The functional properties and underlying mechanisms have been most thoroughly characterized in Ansell's mole-rat, Fukomys anselli, which is the species of choice due to its spontaneous drive to construct nests in the south-eastern sector of a circular arena using the magnetic field azimuth as the primary orientation cue. Due to the remarkable consistency between experiments, it is generally believed that this directional preference is innate. To test the hypothesis that spontaneous south-eastern directional preference is a shared, ancestral feature of all African mole rats (Bathyergidae, Rodentia), we employed the same arena assay to study magnetic orientation in two other mole-rat species, the social giant mole-rat Fukomys mechowii and the solitary silvery mole-rat Heliophobius argenteocinereus. Both species exhibited spontaneous western directional preference and deflected their directional preference according to shifts in the direction of magnetic north, clearly indicating that they were deriving directional information from the magnetic field. Because all of the experiments were performed in total darkness, our results strongly suggest that all African mole rats use a light-independent magnetic compass for near-space orientation. However, the spontaneous directional preference is not common and may be either innate but species-specific, or learned. We propose an experiment that should be performed to distinguish between these two alternatives.
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Niessner C, Denzau S, Gross JC, Peichl L, Bischof HJ, Fleissner G, Wiltschko W, Wiltschko R. Avian ultraviolet/violet cones identified as probable magnetoreceptors. PLoS One 2011; 6:e20091. [PMID: 21647441 PMCID: PMC3102070 DOI: 10.1371/journal.pone.0020091] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Accepted: 04/24/2011] [Indexed: 11/23/2022] Open
Abstract
Background The Radical-Pair-Model postulates that the reception of magnetic compass directions in birds is based on spin-chemical reactions in specialized photopigments in the eye, with cryptochromes discussed as candidate molecules. But so far, the exact subcellular characterization of these molecules in the retina remained unknown. Methodology/Principal Findings We here describe the localization of cryptochrome 1a (Cry1a) in the retina of European robins, Erithacus rubecula, and domestic chickens, Gallus gallus, two species that have been shown to use the magnetic field for compass orientation. In both species, Cry1a is present exclusively in the ultraviolet/violet (UV/V) cones that are distributed across the entire retina. Electron microscopy shows Cry1a in ordered bands along the membrane discs of the outer segment, and cell fractionation reveals Cry1a in the membrane fraction, suggesting the possibility that Cry1a is anchored along membranes. Conclusions/Significance We provide first structural evidence that Cry1a occurs within a sensory structure arranged in a way that fulfils essential requirements of the Radical-Pair-Model. Our findings, identifying the UV/V-cones as probable magnetoreceptors, support the assumption that Cry1a is indeed the receptor molecule mediating information on magnetic directions, and thus provide the Radical-Pair-Model with a profound histological background.
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Affiliation(s)
- Christine Niessner
- Fachbereich Biowissenschaften der J.W. Goethe-Universität Frankfurt, Frankfurt am Main, Germany
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Cerella C, Cordisco S, Albertini MC, Accorsi A, Diederich M, Ghibelli L. Magnetic fields promote a pro-survival non-capacitative Ca2+ entry via phospholipase C signaling. Int J Biochem Cell Biol 2010; 43:393-400. [PMID: 21095240 DOI: 10.1016/j.biocel.2010.11.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Revised: 11/04/2010] [Accepted: 11/15/2010] [Indexed: 11/28/2022]
Abstract
The ability of magnetic fields (MFs) to promote/increase Ca(2+) influx into cells is widely recognized, but the underlying mechanisms remain obscure. Here we analyze how static MFs of 6 mT modulates thapsigargin-induced Ca(2+) movements in non-excitable U937 monocytes, and how this relates to the anti-apoptotic effect of MFs. Magnetic fields do not affect thapsigargin-induced Ca(2+) mobilization from endoplasmic reticulum, but significantly increase the resulting Ca(2+) influx; this increase requires intracellular signal transduction actors including G protein, phospholipase C, diacylglycerol lipase and nitric oxide synthase, and behaves as a non-capacitative Ca(2+) entry (NCCE), a type of influx with an inherent signaling function, rather than a capacitative Ca(2+) entry (CCE). All treatments abrogating the extra Ca(2+) influx also abrogate the anti-apoptotic effect of MFs, demonstrating that MF-induced NCCE elicits an anti-apoptotic survival pathway.
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Affiliation(s)
- Claudia Cerella
- Dipartimento di Biologia, Universita' degli Studi di Roma Tor Vergata, Via della Ricerca Scientifica snc, 00133 Roma, Italy
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The Role of the Magnetite-Based Receptors in the Beak in Pigeon Homing. Curr Biol 2010; 20:1534-8. [PMID: 20691593 DOI: 10.1016/j.cub.2010.06.073] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 06/25/2010] [Accepted: 06/25/2010] [Indexed: 11/21/2022]
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Wiltschko R, Gehring D, Denzau S, Güntürkün O, Wiltschko W. Interaction of magnetite-based receptors in the beak with the visual system underlying 'fixed direction' responses in birds. Front Zool 2010; 7:24. [PMID: 20707905 PMCID: PMC2925349 DOI: 10.1186/1742-9994-7-24] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Accepted: 08/13/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND European robins, Erithacus rubecula, show two types of directional responses to the magnetic field: (1) compass orientation that is based on radical pair processes and lateralized in favor of the right eye and (2) so-called 'fixed direction' responses that originate in the magnetite-based receptors in the upper beak. Both responses are light-dependent. Lateralization of the 'fixed direction' responses would suggest an interaction between the two magnetoreception systems. RESULTS Robins were tested with either the right or the left eye covered or with both eyes uncovered for their orientation under different light conditions. With 502 nm turquoise light, the birds showed normal compass orientation, whereas they displayed an easterly 'fixed direction' response under a combination of 502 nm turquoise with 590 nm yellow light. Monocularly right-eyed birds with their left eye covered were oriented just as they were binocularly as controls: under turquoise in their northerly migratory direction, under turquoise-and-yellow towards east. The response of monocularly left-eyed birds differed: under turquoise light, they were disoriented, reflecting a lateralization of the magnetic compass system in favor of the right eye, whereas they continued to head eastward under turquoise-and-yellow light. CONCLUSION 'Fixed direction' responses are not lateralized. Hence the interactions between the magnetite-receptors in the beak and the visual system do not seem to involve the magnetoreception system based on radical pair processes, but rather other, non-lateralized components of the visual system.
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Affiliation(s)
- Roswitha Wiltschko
- Fachbereich Biowissenschaften der J, W, Goethe-Universität, Siesmayerstrasse 70, D-60054 Frankfurt am Main, Germany.
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Biro D. Bird Navigation: A Clear View of Magnetoreception. Curr Biol 2010; 20:R595-6. [DOI: 10.1016/j.cub.2010.05.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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