pigeonThey undertake some of the most audacious journeys in the animal kingdom, navigating across thousands of miles to arrive at a precise location.

Now scientists have unravelled exactly how migrating birds, butterflies and other animals are able to use the Earth’s magnetic field to help them find their way.

They have discovered proteins that ‘act like a compass’ are produced in the retina and nerve cells running from the eye to the brain.

Pigeons are known for their navigational ability but now scientists claim to have discovered the molecules the birds use to find their way. The animals, along with many other species, have proteins that form a rod-shaped complex that orientate themselves in a north to south direction in the Earth’s magnetic field

These molecules form a rod-like complex with light sensitive proteins and orientate themselves in a north to south direction in a magnetic field.

Together, this complex allows the animals to sense the direction they are travelling by combining information about the Earth’s magnetic field and the position of the sun.

Long-distance songbirds perform incredible feats of navigation during their spring migration.

While scientists know the birds use the sun or stars as a ‘map,’ the idea that birds use magnetic compasses has been difficult to prove.

Now a group of researchers have used a magnet to deliberately send Eurasian reed warblers off course, to show they rely on a geomagnetic map cues to point them in the right direction.

In the experiment, the birds were captured at Rybachy, Russia, during their spring migration.

To test the role of magnetic fields, Dmitry Kishkinev of Queen’s University Belfast and Nikita Chernetsov at the Biological Station Rybachy housed caught birds outdoors in wooden and cloth cages so they had a clear view of the sky and their surroundings.

They observed the birds naturally orientated north-east, which matches the chosen direction of migration recorded over the previous decade.

They then generated a magnetic field identical to that found in the town of Zvenigorod near Moscow.

The system allowed them to manipulate the magnetic field without obscuring the birds’ ability to pick up on other cues, including the sun, stars, landmarks, and scents, which are also thought to help birds find their way across vast distances.

During the several days that the birds were housed in the magnetic coil system, they were led to ‘think’ they were in Zvenigorod, some 621 miles (1,000km) away.

Perhaps most astonishingly, the researchers discovered that humans also express these same proteins, albeit in far smaller amounts, raising the prospect that we too have some ability to sense the magnetic field.

Dr Can Xie, a molecular biologist at Peking University in China who led the research, said the proteins appear to act just like a compass needle and send information to the nervous system.

Writing in the journal Nature Materials, Dr Xie and his colleagues said: ‘The notion that animals can detect the Earth’s magnetic field was once ridiculed, but is now well established.

‘The biocompass model we present here may serve as a step towards fully uncovering the molecular mechanism of animal navigation and magnetoreception.

‘The existence of a human magnetic sense remains controversial but geomagnetic fields are thought to affect the light sensitivity of the human visual system.’

Many animals are thought to use the Earth’s magnetic fields to help them navigate including sharks, sea turtles, birds, insects, wolves, whales and even worms.

However, exactly how they do this has remained a mystery.

Some researchers previously identified specific cells in the eyes and beaks of birds like pigeons that seem to respond to a magnetic field.

The exact source was unknown, and some researchers identified clumps of iron bound by molecules as being responsible, while others attributed it to light-sensitive proteins called cyrptochromes.

The research by Dr Xie and his team, however, has found that these two systems in fact work together to form a navigational complex inside the cells of these animals.

In particular, they discovered a gene called MagR that produces a protein that combines with cryptochrome to form a cylinder shaped complex.

Ten cryptochrome molecules encase 20 MagR proteins to form this rod that then aligns itself with a magnetic field.

They were so magnetic that the researchers had to develop special plastic tools to conduct their research

Insects, including monarch butterflies (pictured) were also found to produce the proteins to help them navigate. Monarch butterflies undertake one of the greatest migrations on the planet, travelling up to 3,100 miles

The scientist found these molecules are particularly highly expressed in the retinal neurons running from the eye to the brain.

Fruit flies, monarch butterflies, pigeons and humans all produce these molecules while other creatures including minke whales and naked mole rats also have these magnetic proteins.

The researchers say their findings may also now lead to a new area of research that could have numerous biological and industrial applications.

It could lead to new types of genetic treatments that respond to magnetic fields or ways of increasing magnetic sensitivity.

The MagR proteins form a magnetic core inside a coat of light sensitive cryptochrome molecules (Crys) to form a cylinder. The graphic above shows how they orientate in the complex on the left while the diagram on the right shows the cylinder of proteins in a cross section
The MagR proteins form a magnetic core inside a coat of light sensitive cryptochrome molecules (Crys) to form a cylinder. The graphic above shows how they orientate in the complex on the left while the diagram on the right shows the cylinder of proteins in a cross section

They said: ‘It has not escaped our notice that the magnetic features of the MagR polymer and Cry/MagR complex may provide a useful tool for the isolation and manipulation of macromolecules with external magnetic fields, give rise to magnetogenetics and inspire numerous potential applications across different fields.’

Dr Steven Reppert, a neurobiologist at the University of Massachusetts who was not involved in the research, told New Scientist that the research could have huge implications.

He said: ‘It’s provocative and potentially ground breaking. It took my breath away.’


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