Department of Earth and Environmental Sciences, Ludwig-Maximilians-University, 80333 Munich, Germany.
J R Soc Interface. 2010 Apr 6;7 Suppl 2(Suppl 2):S273-89. doi: 10.1098/rsif.2009.0435.focus. Epub 2010 Jan 19.
Although ferrimagnetic material appears suitable as a basis of magnetic field perception in animals, it is not known by which mechanism magnetic particles may transduce the magnetic field into a nerve signal. Provided that magnetic particles have remanence or anisotropic magnetic susceptibility, an external magnetic field will exert a torque and may physically twist them. Several models of such biological magnetic-torque transducers on the basis of magnetite have been proposed in the literature. We analyse from first principles the conditions under which they are viable. Models based on biogenic single-domain magnetite prove both effective and efficient, irrespective of whether the magnetic structure is coupled to mechanosensitive ion channels or to an indirect transduction pathway that exploits the strayfield produced by the magnetic structure at different field orientations. On the other hand, torque-detector models that are based on magnetic multi-domain particles in the vestibular organs turn out to be ineffective. Also, we provide a generic classification scheme of torque transducers in terms of axial or polar output, within which we discuss the results from behavioural experiments conducted under altered field conditions or with pulsed fields. We find that the common assertion that a magnetoreceptor based on single-domain magnetite could not form the basis for an inclination compass does not always hold.
尽管铁磁性材料似乎适合作为动物磁场感知的基础，但目前尚不清楚磁性颗粒如何将磁场转换为神经信号。假设磁性颗粒具有剩余磁化强度或各向异性磁导率，那么外部磁场将施加一个扭矩，并可能使其物理扭曲。文献中已经提出了几种基于磁铁矿的此类生物磁扭矩传感器模型。我们从第一性原理出发分析了它们可行的条件。基于生物单畴磁铁矿的模型证明是有效且高效的，无论磁结构是否与机械敏感离子通道耦合，还是与利用磁结构在不同场方向产生的杂散场的间接转换途径耦合。另一方面，基于前庭器官中多畴磁性颗粒的扭矩探测器模型被证明是无效的。此外，我们还提供了一种基于轴向或极轴输出的扭矩传感器通用分类方案，并在该方案中讨论了在改变的磁场条件下或使用脉冲磁场进行的行为实验的结果。我们发现，基于单畴磁铁矿的磁受体不可能构成倾斜罗盘基础的常见说法并不总是成立。
