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Biophys. J. BioFAST: First Published April 29, 2005. doi:10.1529/biophysj.104.049346
© 2005 by the Biophysical Society.

A more recent version of this article appeared on July 1, 2005.
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BIOPHYSICAL THEORY AND MODELING

Magnetic pulse affects putative magnetoreceptor mechanism

Alfonso F Davila 1, Michael Winklhofer 1*, Valera P Shcherbakov 2 and Nikolai Petersen 1

1 Department of Earth and Environmental Science, University of Munich
2 Geophysical Observatory Borok, Russian Academy of Science

* To whom correspondence should be addressed. E-mail: michaelw{at}lmu.de.

Submitted on July 12, 2004
Revised on August 21, 2004
Accepted on 29 March 2005


  Abstract
Clusters of superparamagnetic (SP) magnetite have recently been identified in free nerve endings in the upper-beak skin of homing pigeons and are interpreted as being part of a putative magnetoreceptor system. Motivated by these findings, we developed a physical model that accurately predicts the dynamics of interacting SP clusters in a magnetic field. The main predictions are: 1) Under a magnetic field, a group of SP clusters self-assembles into a chain-like structure that behaves like a compass needle under slowly rotating fields; 2) in a frequently changing field as encountered by a moving bird, a stacked chain is a structurally more stable configuration than a single chain; 3) chain-like structures of SP clusters disrupt under strong fields applied at oblique angles, and 4) re-assemble on a time scale of hours to days (assuming a viscosity of the cell plasma {eta} ~ 1 P). Our results offer a novel mechanism for magnetic field perception and are in agreement with the response of birds observed after magnetic-pulse treatments, which have been conducted in the past to specifically test if ferrimagnetic material is involved in magnetoreception, but which have defied explanation so far. Our theoretical results are supported by experiments on a SP model system using a high-speed camera. We also offer new predictions that can be tested experimentally.

Key Words: ferrofluids, free nerve endings, homing pigeon, magnetoreception, migratory birds, orientation




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Copyright © 2005 by the Biophysical Society.