Can a hybrid chemical-ferromagnetic model of the avian compass explain its outstanding sensitivity to magnetic noise?

Kirill Kavokin,Ilia Solov'Yov

doi:10.1371/journal.pone.0173887

Abstract

While many properties of the magnetic compass of migratory birds are satisfactory explained within the chemical model of magnetoreception, its extreme sensitivity to radio-frequency magnetic fields remains a mystery. Apparently, this difficulty could be overcome if the magnetoreceptor model were augmented with a magnetite nanoparticle, which would amplify the magnetic field at the position of the magneto-sensitive cryptochrome molecule. However, comparison of the radio-frequency power used in the experiment with intrinsic magnetization noise of such a particle, estimated from the theory of fluctuations, shows that the required sensitivity cannot be reached with realistic parameters of iron-oxide nanocrystals.

Highlights

The magnetic sense and its use by various animals for orientation and navigation is one of the hot topics of research in sensory physiology and behavioral zoology [1]
By applying to a bird in the test cage a weak magnetic field oscillating at the frequency close to electron spin resonance in the static ambient field, the experimentalists were able to disrupt the bird’s ability to orient
If magnetic moments of the two electrons are equal to each other external magnetic fields do not cause transitions between singlet and triplet states, which are eigenstates of the total spin operator of the electron pair [27]

Summary

Introduction

The magnetic sense (magnetoreception) and its use by various animals for orientation and navigation is one of the hot topics of research in sensory physiology and behavioral zoology [1]. In one case, namely the compass receptor of migratory birds, non-trivial quantitative information was obtained in a series of intricate behavioural tests. This experimental approach, designed and realized in the group of R. and W. By applying to a bird in the test cage a weak magnetic field oscillating at the frequency close to electron spin resonance in the static ambient field, the experimentalists were able to disrupt the bird’s ability to orient. The disruptive effect of the oscillating field was found to be sensitive to its frequency; this method can be called spectroscopy

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