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Special Molecule Gives Birds a Magnetic Biocompass
Aaron Rowe writes "CORDIS news reports that a team of scientists has identified a family of molecules called cryptochromes that allow migratory birds to sense magnetic fields. Curiously enough, these molecules only function when accompanied by blue light. The article also mentions, 'The researchers also suggest that, as cryptochromes have been strongly conserved throughout evolution, all biological organisms could have the ability to detect magnetic fields, even if they do not use them.'"
Lost in the woods... nothing to make a shadow with...
r-i-g-h-t.
thank you for the chuckle.
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I will dispute their statement about pigeons though. I recall watching or reading something where the scientists put trackers on homing pigeons to discover how they found their way around. Turns out they follow landmarks.
The pigeons often took indirect routes, because they were following a road. The scientists didn't figure this out even after they realized the paths were very odd... it didn't click until someone looked at a road map.
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o0t!
The same thing happened to me once, when I was working to prepare an MRI scanner for an experiment. There was a radiologist there, so I asked him what the mechanism was, and he said it was believed that the magnetic fields affect metal ions in your otoliths, which are the organs in the inner ear responsible for sensing motion. Apparently it's known that some fish and birds have magnetic materials in their otoliths, but I'm not sure if it's ever been demonstrated directly in humans.
Also, it's known that the brain can be directly stimulated with strong magnetic fields, as in transcranial magnetic stimulation.
Note that while the magnetic moments are being manipulated, the actual water molecules themselves are more or less unaffected. This is one reason that MRI/NMR is such a great way to measure molecular self-diffusion- the phenomenon of diffusion is unaffected by all the magnetic fields being bandied about the sample. So to sum up, the "torque" the water molecules experience is one that affects only the magnetic orientation of the hydrogen atoms in your body, and not the actual physical orientation. And the signal that an MRI machine detects is not coming from the return to equilibrium of the water molecules as much as it comes from the precession of the asffected magnetic moments about the direction of the external field.
Blue light? This is possibly a stupid question, but isn't sunlight yellow?
Yes, but skylight is blue.
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I think you've just hit upon a new theory as to why the dinosaurs went extinct. Is there any evidence, for or against? How well are the dinosaur extinction event and the magnetic pole flips narrowed down, and could the dinosaur extinction be a delayed reaction?
Well, the thing is, magnetic pole reversals actually happen pretty often, according to Wikipedia at a rate of 1-5 events every million years. Since the dinosaurs lived 65-230 million years ago, by looking at this graph we can deduce that during their existence they experienced a few dozen pole reversals.
Now that I look at it though, it is somewhat interesting that the Cretaceous Long Normal, an abnormally long (~40 million year) period during which there were no pole reversals at all, ended around 15 million years before the dinosaurs disappeared. I personally think it's just a coincidence, though.
It's a very badly written press release. In fact the actual science has zilch to do with birds and everything to do with plants using the same molecule. They described the way light and magnetic fields interact to change the way the plant stem grows, except in plants without the cryptochrome molecule.
Which is just basic, everyday scientific advancement: a very small and excruciatingly dull thing, presented with a tie-in to something more interesting in an attempt to look sexier and get funding. Scientists hate doing it, but if you want to keep doing science, that's what you do.
This article IS news, but only in the narrowest sense: new information. But after you take that new information, tie it in to something more interesting but only indirectly related (which you put at the front of the press release, and the actual new stuff at the end), then summarize it for Slashdot (skipping the stuff at the end), "news" becomes "olds".
One final note: when I call the work "small", I don't mean to dis the grad students who worked thousands of hours tending the plants, measuring them, putting that data into the computer, analyzing that data, probably cutting them open and measuring that... such immense grunt work for a minor advance [promptly blown up into something irrelevant by university's press department] is the heavy-lifting of science. It's gotta be done but it's not glamorous or even interesting.
Is it because we have learned how to use magnetics for navigation, so we therefore assume that animals capable of sensing magnetic fields must use it for navigation as well? The problem is that this is a false assumption.
--Birds can sense magnetic information. However, when the olfactory nerve is cut, they get lost even when the trigeminal nerve remains intact. Birds which have had the trigeminal nerve cut but which had the olfactory nerve left intact could find their way home. So the claim is that being able to sense magentic fields was not required for homing pigeons.
Still, it is generally accepted that homing pigeions have the wetwork required to sense magnetic fields. And if not used for navigation, then what? Why did such a sense develop?
Put another way, what other perceptive planes of information exist which might make being able to sense EM fields useful?
ALL organisms might have this ability?
Chi-wiz.
-FL
The phrasology may be off, but the sentiment is there. Having hiked in the woods on an overcast day it is very difficult to make out where the sun is. The light is very diffuse and omni-directional. I agree though that "nothing to make shadows with" is not the best way to express diffused light.
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