Winklhofer, Michael; Kirschvink, Joseph L.
A quantitative assessment of torque-transducer models for magnetoreception.
In: Journal of the Royal Society Interface, Vol. 7, No. 2: S273-S289
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Although ferrimagnetic material appears suitable as a basis of magneticfield perception in animals, it is not known by which mechanism magneticparticles may transduce the magnetic field into a nerve signal. Providedthat magnetic particles have remanence or anisotropic magneticsusceptibility, an external magnetic field will exert a torque and mayphysically twist them. Several models of such biological magnetic-torquetransducers on the basis of magnetite have been proposed in theliterature. We analyse from first principles the conditions under whichthey are viable. Models based on biogenic single-domain magnetite proveboth effective and efficient, irrespective of whether the magneticstructure is coupled to mechanosensitive ion channels or to an indirecttransduction pathway that exploits the strayfield produced by themagnetic structure at different field orientations. On the other hand,torque-detector models that are based on magnetic multi-domain particlesin the vestibular organs turn out to be ineffective. Also, we provide ageneric classification scheme of torque transducers in terms of axial orpolar output, within which we discuss the results from behaviouralexperiments conducted under altered field conditions or with pulsedfields. We find that the common assertion that a magnetoreceptor basedon single-domain magnetite could not form the basis for an inclinationcompass does not always hold.