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European Biophysics Journal

, Volume 28, Issue 5, pp 380–392 | Cite as

The osmotic magnetometer: a new model for magnetite-based magnetoreceptors in animals

  • Valera P. Shcherbakov
  • M. Winklhofer
ARTICLE

Abstract

Homing pigeons and migratory birds are well known examples for animals that use the geomagnetic field for their orientation. Yet, neither the underlying receptor mechanism nor the magnetoreceptor itself is known. Recently, an innervated structure containing clusters of magnetite nanocrystals was identified in the upper beak skin of the homing pigeon. Here we show theoretically that such a cluster has a magnetic-field-dependent shape, even in fields as weak as the Earth's magnetic field; by converting magnetic stimuli into mechanical strain, the clusters can be assumed as primary units of magnetoperception in homing pigeons. Since the orientation of the strain ellipsoid indicates the direction of the external magnetic field, a cluster of magnetite nanocrystals also has the potential to serve as the basis of the so-called inclination compass of migratory birds. It is quantitatively demonstrated that the magnetic-field-induced shape change of a cluster can be amplified as well as counterbalanced by means of osmotic pressure regulation, which offers an elegant possibility to determine the magnetic field strength just by measuring changes in concentration.

Key words Superparamagnetism Magnetic fluids Ferrovesicle 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Valera P. Shcherbakov
    • 1
  • M. Winklhofer
    • 2
  1. 1.Geophysical Observatory “Borok”, Borok Yaroslavskaja oblast, 151742, RussiaRU
  2. 2.Institut für Geophysik der Ludwig-Maximilians-Universität München, Theresienstrasse 41, D-80333 München, Germany e-mail: michael@alice.geophysik.uni-muenchen.deDE

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