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.'"

Comments

Iron in your nose

[TubeSteak]

According to http://everything2.com/index.pl?node=nose

• There's a compass in my nose?
  
  
• All humans have a trace amount of iron in their noses, a rudimentary compass found in the ethmoid bone (between the eyes) to help in directional finding relative to the earth's magnetic field.
  
  
• Studies show that many people have the ability to use these magnetic deposits to orient themselves-even when blindfolded and removed from such external clues as sunlight-to within a few degrees of the North Pole, exactly as a compass does.
  
  
• Though no one knows how this "sixth" sense is processed by the brain more then two dozen animals, including the dolphin, tuna, salmon, salamander, pigeon, and honeybee have been found to have similar magnetic deposits in their brains to help them in navigation and migration.

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.

Re:Detecting Changing Magnetic Fields

[DrLudicrous]

You are right in some respects. The moment to which you refer is the nuclear magnetic moment of the hydrogen atom, which are quite plentiful in most living things, ourselves included, due to the prevalence of water. In MRI, the torque these moments experience causes them to change their alignment from being in the same direction as an externally applied magnetic field (hence the big MRI magnet), to one that lies perpendicular to the direction of the external field. As they do this, the precess about the external field axis at a rate called the "Larmor frequency" (i.e. they rotate about it). This causes the magnetic flux inside the MRI receiver coil (more or less a loop of wire) to change, and by Lenz's Law, an EMF (voltage) will be induced. This is the signal that is detected.

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.

Re:Extinction

[FleaPlus]

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.

There is news, very small and buried at the end

[Alfred, Lord Tennyso]

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.