Birds Can See Earth's Magnetic Fields, And Now We Know How That's Possible
"Birds can use two kinds of information from the geomagnetic field for navigation: the direction of the field lines as a compass and probably magnetic intensity as a component of the navigational ‘map’. The direction of the magnetic field appears to be sensed via radical pair processes in the eyes, with the crucial radical pairs formed by cryptochrome (from the Greek κρυπτός χρώμα, "hidden color") are a class of flavoproteins that are sensitive to blue light. They are found in plants and animals. Cryptochromes are involved in the circadian rhythms of plants and animals, and the sensing of magnetic fields in a number of species). It is transmitted by the optic nerve to the brain, where parts of the visual system seem to process the respective information". Source/Credit : royalsocietypublishing.org
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Ability to perceive magnetism is called “magnetoreception." We know from behavioral evidence that many organisms, from bacteria, to lobsters, to pigeons sense and respond to magnetic fields but we are just starting to learn how this works. II. involvement of Cry4 in light-
dependent magnetoreception:
The Lund team measured gene expression of three cryptochromes, Cry1, Cry2 and Cry4, in the brains, muscles and eyes of zebra finches. Their hypothesis was that the cryptochromes associated with magnetoreception should maintain constant reception over the circadian day. They found that, as expected for circadian clock genes, Cry1 and Cry2 fluctuated daily - but Cry4 expressed at constant levels, making it the most likely candidate for magnetoreception. II. protein in the eye: Cry 4
The mystery behind how birds navigate might finally be solved: it's not the iron in their beaks providing a magnetic compass, but a protein in their eyes that lets them "see" Earth's magnetic fields. These findings come courtesy of two papers - one studying robins, the other zebra finches. The fancy eye protein is called Cry4, and it's part of a class of proteins called cryptochromes - photoreceptors sensitive to blue light, found in both plants and animals. These proteins play a role in regulating circadian rhythms. |
I of V :: theory of magnetoreception & cry 4 protein navigation
III of V: Protein in the eye: Cryptochromes ( Cry 4 )
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III. where do they go?
As winter approaches, V-shaped flocks glide overhead as the world's birds begin their long treks to warmer climates. Humans used to have some pretty crazy theories about where birds went for winter, like the moon, or to the bottom of the ocean! IV. So what do they see?
Well, we can't ever know what the world looks like through another species' eyes, but we can take a very strong guess. According to researchers at the Theoretical and Computational Biophysics group at the University of Illinois at Urbana-Champaign, whose researcher Klaus Schulten first predicted magnetoreceptive cryptochromes in 1978, they could provide a magnetic field "filter" over the bird's field of view - like in the picture to the right: Both sets of researchers caution that more research is needed before Cry4 can be declared the protein responsible for magnetoreception. The evidence is strong, but it's not definitive, and both Cry1 and Cry2 have also been implicated in magnetoreception, the former in garden warblers and the latter in fruit flies. Observing birds with non-functioning Cry4 could help confirm the role it seems to play, while other studies will be needed to figure Cry1's role.
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IV of V: History of Study of bird migration
V of V: So what does a bird actually see?
VI : TIM Blais - Deep science. Sweet harmony
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