Many migratory species use the Earth’s magnetic field to stay on track during their journey. But a study of the non-migratory Drosophila fruit fly shows that the same ability exists in some unexpected creatures. In fact, we may be the rare and strange ones, perhaps because we as humans do not have this ability.
In the pursuit of survival, access to information about the world, especially information that your competitors do not have, is extremely valuable. It’s no surprise, therefore, that animals have developed an astonishing array of methods for observing the world around them. Magnetic fields are also one of these methods, but humanity’s ability to detect them before the invention of powerful electromagnets was generally very weak. The effort required to detect magnetic fields was much greater than that required for light or sound.
As a result, biologists thought that only animals that really needed to know their place on Earth, such as migratory pigeons or turtles, benefited from magnetoreception. But an article in Nature questions this.
The possibility that Drosophila might have the ability to sense magnetic fields emerged in 2015 with the identification of a MagR protein produced by flies that orients itself to align with magnetic fields.
The newly published paper goes a step further by showing two methods by which fly cells can detect magnetic fields. Previous work identified photoreceptor proteins known as cryptochromes as sensors used by Drosophila to detect domains. In flies that were apparently designed not to produce cryptochromes, this ability failed, leaving them magnetically blind.
The authors of the new paper point to work showing that cryptochromes do this by harnessing the powers of quantum superpositioning. But at the same time, the team also questions the need for cryptochromes, showing that their role can be replaced by a molecule found in all living cells, including humans.
From the US National Physics Laboratory, Dr. “The absorption of light by the cryptochrome causes an electron to move within the protein, which, due to quantum physics, can form an active form of cryptochrome occupying one of the two states,” Alex Jones said in a statement. The presence of a magnetic field affects the relative populations of the two states, which in turn affects the ‘active lifetime’ of this protein,” he says.
The authors showed that the flavin adenine dinucleotide (FAD) molecule binds to cryptochromes, creating their susceptibility to magnetism. They also found that cryptochromes can be an amplifier of the capacity of the FAD, not necessary for it.
Even without cryptochromes, fly cells engineered to express extra FAD were able to respond to the presence of magnetic fields and were highly sensitive to blue light in the presence of these fields. The magnetoreception required no more than electron transfer to a side chain. The authors think cryptochromes may have evolved to take advantage of this.
“This study may allow us to better assess the potential effects of magnetic field exposure on humans,” says co-author Professor Ezio Rosato of the University of Leicester.
In addition to perceiving magnetic fields, migratory animals can also sense their direction because these fields have different angles. It is still unknown whether flies benefit from this information or whether this is a trait inherited from a migratory ancestor.
The article was published as open access in Nature.
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