Birds Can See Earth's Magnetic Fields, And Now We Know How That's Possible
I. 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 IV. The study from Lund University in Sweden:II of IV: 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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III of IV: History of Study of bird migration
IV of IV: So what does a bird actually see?
V : TIM Blais - Deep science. Sweet harmony
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