Small animal whiskers can act as sensitive compass needles

Steriocilia bundles into the inner ear. credit: KV Kavokin; EPJ ST

Statistical mechanics shows that some animals may be able to perceive the Earth’s magnetic field with bundles of microscopic hairs in their inner ears.

The exact mechanisms that animals use to sense the direction of Earth’s magnetic field have long been a mystery. One leading theory suggests that this ability is linked to microscopic beams hair cells in the inner ears. Through a new research published in Topics for the European Physical JournalKirill Cavukin at St. Petersburg State University, Russia, uses statistical analysis To demonstrate that about 100 of these hair cells can act as effective biological compass needles, allowing this the animals To accurately sense the magnetic field around them.

This unique sensing ability called “magnetic reception” is found across a wide range of vertebrate species: from migratory birds to burrowing rodents. Several mechanisms have been proposed to explain this ability – but despite more than 50 years of research, none have been definitively observed in nature.

One leading theory is based on bundles of hair cells in the inner ear, called ‘stereocilia’. According to this idea, stereocilia are attached to magnetite nanocrystals: an iron-based mineral that can become permanently magnetized, corresponding to the Earth’s magnetic field. As the orientation of the animal changes, the magnetite forces changes in the orientations of the stereocilia associated with it. These changes can then be picked up by mechanoreceptors: neurons that can detect mechanical stress – providing the animal with a physical sense of magnetic field. However, it is uncertain whether this nervous cells Sensitive enough to detect such subtle changes.

To explore this idea further, Cavukin studied the fluctuations of ariocilia under Statistical mechanicswhich applies the mathematical language of statistics to large groups of microscopic organisms.

Through his analysis, Kavokin showed that strocilia bundles can indeed act as highly sensitive compass needles, with only about 100 hair cells required for mechanoreceptors to pick up their fluctuations. This intriguing finding could bring biologists a step closer to understanding the origins of magnetic reception, and ultimately identifying the mechanisms responsible in nature.

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more information:
KV Kavokin, Compass in the ear: Can animals sense magnetic fields in hair cells?, Topics for the European Physical Journal (2022). DOI: 10.1140/epjs/s11734-022-00654-y

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