Trout shows animals use magnetic sense to navigate

Scientists have identified what they say are tiny compass needles in the noses of rainbow trout which could help explain these and many other animals’ incredible ability to navigate across vast distances.

Researchers at the University of Munich in Germany found cells in the trout’s nasal passages that respond to magnetism.

When the cells were were placed in a rotating magnetic field, a clump of tiny iron-rich crystals inside the cells called magnetite spun in synchrony with the field, turning the cells around with them, the researchers said. “More importantly, we show for the first time that the internal compass needle has a strong connection to the plasma membrane [or outer membrane] of the cell, which is important to realise an immediate sensing process,” Michael Winklhofer, who led they study, was quoted as saying by LiveScience.

The results, detailed in the journal Proceedings of the National Academy of Sciences, showed that the magnetic cells “clearly meet the physical requirements for a magnetoreceptor” capable of rapidly detecting small changes in earth’s magnetic field, the researchers said. The strength of earth’s field varies in a predictable way across the planet’s surface, allowing migratory animals to use it for position-finding. By learning the strength of a field that exists at a particular destination, the animals can home in on it.

The researchers also said their discovery also opened up avenues for all sorts of futuristic applications, including miniaturised Global Positioning System (GPS) systems or gene therapies that would restore sight, hearing or smell to people who have lost those senses.

The ability to detect magnetic-sensitive cells in the lab could also help answer questions about whether people are at risk from magnetic fields produced by power lines and other equipment, they said. Kenneth Lohmann, a biology professor at the University of North Carolina who studies animals’ magnetic sense, said the findings have ramifications beyond the realm of rainbow trout.

“If the authors are correct that the magnetite they have found is involved in detecting magnetic fields (which seems likely), then... this might have important implications for how other animals perceive magnetic fields,” Lohmann said.

“It is quite possible that similar magnetite crystals are involved in detecting magnetic fields in numerous animals.” It is also possible that there are two or more types of magnetoreceptors that evolved separately, he said.