Many species, including insects, sea turtles and migratory birds, use Earth’s magnetic field for orientation and navigation. Their ability to carry out magnetoreception is often believed to be due to rotating magnetic nanoparticles found in their bodies that work similarly to a compass needle.
Studying American cockroaches, Asst Prof Tomasz Paterek and Assoc Prof Rainer Dumke of NTU’s School of Physical and Mathematical Sciences showed that magnetic nanoparticles behave very differently in living and dead animals—in dead animals, the particles’ magnetisation dynamics decline due to dehydration.
Using a customised and highly sensitive atomic magnetometer to detect the magnetic deposits in the insects’ bodies, the researchers also discovered that the nanoparticles cannot be responsible for magnetic field-sensing and navigating, as the viscous environment renders the magnetic compasses too slow to be of biological significance.
“Our experiment points to other mechanisms of magnetoreception—for instance, the radical-pair mechanism in which a magnetic field influences the outcome of a chemical reaction,” says Asst Prof Paterek.
Their findings are an important step in the long-standing puzzle of how animals sense magnetic fields—including whether humans are able to do the same—and may help in the development of bio-inspired magnetic sensors, the researchers say.