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29.003 Birds can see the magnetic field of the earth

 

Die Welt
So can birds see the magnetic field of the earth, 05.04.2018
welt.de, Birds can see the magnetic field of the earth

 

Welt

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Amazing!

So can birds see the magnetic field of the earth

Julia Haase

5. April 2018

Who looks up in these days will now and then see migratory birds in formation. They mostly come from the other end of the world. A research team has now found out how they then get their bearings: They can obviously see magnetic fields.

Where do birds know from where they fly? How do they get their bearings? The mystery about navigation of blackbird, finch and eagle keeps men busy since there are carrier pigeons. What one assumed up to now, is that they use the magnetic field for getting their bearings; they can feel it.

Researchers assumed up to now that they measure the strength of the magnetic field with iron rich cells in their beak and so get their bearings. But it is not iron in the beak, which is responsible for the magnetic compass. It is still more complex!

Biologists of the Carl von Ossietzky University Oldenburg and of the University Lund in Sweden have discovered a protein in the eyes of birds, which makes it possible for them to actually see the magnetic fields.

The researchers in Sweden have investigated 39 zebra finches for their study.

The ingenious protein in the eye is called Cry4 and belongs to a class of proteins, which are called crypto chromes photo receptors, which are sensitive to blue light and occur both in plants and also in animals. These crypto chromes play a role in the regulation of the circadian rhythms, therefore of the biological sleep cycles.

The team of the Swedes has measured the development of three crypto chromes - Cry1, Cry2 and Cry4 - in the brains, muscles and eyes of zebra finches. The hypothesis was that the crypto chromes, which are associated with the magnetic reception, must maintain a constant reception over the day night rhythm.

On that occasion it turned out that Cry1 and Cry2 varied daily, but Cry4 remained lastingly constant.

The researchers inferred from it that Cry4 is responsible for the magnetic reception, therefore for the magnetic sense.

The biologists from Oldenburg found very similar discoveries with the investigation of the European robin.

We take it as our starting point that birds use magnetic compasses at any day and night time. Rachel Muheim, Biologist, University Lund, Sweden

The biologists from Oldenburg could establish in addition that the protein Cry4 is focussed in a region of the retina, which receives much light what is sensible for the light depending magnetic receptors. Earlier studies have already shown that the magnetic sense depends on blue light. Birds can only perceive magnetic fields, when certain wave lengths of light are available.

Moreover the German researchers could prove that the European robin produces more Cry4 proteins in the time of the flight of birds than chickens, which for example do not fly to the south.

But before the protein Cry4 can really mainly be held responsible for the magnetic reception, still more studies and investigations are needed according to both research groups. The proofs indeed strongly indicate it, though the role of Cry1 and Cry2 on the magnetic sense of birds must still be closer investigated. On that occasion the observation of birds with non-functioning Cry4 proteins could help.

When the researchers are right with their discovery, it would be the first time that a specific molecule was identified in animals, which is responsible for the tracking down of magnetic fields.

 

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