Neuroanatomie der Magnetsinne in Zugvögeln
Zusammenfassung der Projektergebnisse
Migratory birds show impressive navigational capabilities on their biannual journeys between breeding and wintering grounds. Since about 50 years it is known that they can use the Earth´s magnetic field as an orientational cue. Initially based on purely behavioural experiments, in recent years, interdisciplinary research proved being instrumental in investigating the sensory correlates underlying the phenomenon of magnetoreception. By now, two mutually not exclusive theories have become established as the most promising magnetoreception systems: (1) a magnetic “compass” sense based on radical-pair forming molecules implemented in the visual system, and (2) a trigeminal-based magnetic sense, whose underlying sensory correlates and biological function have remained elusive yet. Using neuroanatomical and microsurgical techniques together with the analysis of magnetic fieldtriggered neuronal activation patterns (reflected as increased expression of immediate early genes, such as Egr-1), the project “Neuroanatomy of the magnetic senses in migratory birds” aimed to answer key questions related to the neuronal correlates of both magnetic senses. We were able to give bold evidence for the involvement of the trigeminal system in magnetoreception. In pigeons, we showed that the trigeminal brainstem nuclei are activated by magnetic fields and that this magnetic information is mediated via the ophthalmic branch of the trigeminal nerve (V1). In migratory reed warblers, V1-perceived information seems to provide positional information, which the birds used to detect a geographical displacement. Virtual magnetic “displacements” unequivocally showed that reed warblers can use geomagnetic cues only to determine their geographical position. These studies strongly indicate that information from the trigeminal system is used to genererate a magnetic “map”. We were able to implement a visual forebrain region called “Cluster N”, which previously has been shown to be most likely involved in processing magnetic compass information, into the avian forebrain connectivity network. Based on the findings from both putative magnetosensory systems, we made educated speculations how and where in the bird brain magnetic information in being processed, and how maps and compasses are likely to be integrated to compute navigational goals and directions. These claims will be part of future projects in order to investigate the neuronal correlates underlying magnetoreception in birds.
Projektbezogene Publikationen (Auswahl)
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2013. Migratory reed warblers need intact trigeminal nerves to correct for a 1000 km displacement. PloS ONE 8(6): e65847
Kishkinev D, Chernetsov N, Heyers D, Mouritsen H
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2013. The discovery of an iron-rich organelle in the culticular plate of avian hair cells. Current Biology Apr 24
Lauwers M, Pichler P, Edelman N, Ushakova L, Salzer MC, Heyers D, Saunders M, Shaw J, Keays DA
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2014. Magnetic fielddriven induction of ZENK in the trigeminal system of pigeons (Columba livia). Journal of the Royal Society Interface November 6;11: 20140777
Lefeldt N, Heyers D, Schneider NL, Engels S, Elbers, D, Mouritsen H
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2015. Eurasian reed warblers compensate for virtual magnetic displacement. Current Biology 25: R1-R2
Kishkinev D, Chernetsov N, Pakhomov S, Heyers D, Mouritsen H
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2016. Localization of the putative magnetoreceptor Cryptochrome 1b in the retinae of migratory birds and homing pigeons. PloS ONE Mar 8;11(3):e0147819
Bolte P, Bleibaum F, Einwich A, Günther A, Liedvogel M, Heyers D, Depping A, Wöhlbrand L, Rabus R, Janssen-Bienhold U, Mouritsen H
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2016. The neural basis of long-distance navigation in birds. Review. Annual Review of Physiology. Feb 10;78:133-5
Mouritsen H, Heyers D, Güntürkün O
