This is simply fascinating. I heard about it on NPR. While it is well known that birds are sensitive to the earth’s magnetic field, and use it to navigate, apparently it’s only been recently shown that this sensitivity is connected directly to the visual system (at least in some birds). The idea seems to be that the bird has evolved a mechanism for essentially seeing the magnetic field, presumably in the sense that magnetic information is encoded in the visual field and mapped to the brain along with the usual visual data. (Image: A garden warbler, photographed by Tommy Holden. I found it on the British Trust for Ornithology website, here.)
Have a listen to the NPR interview with Henrik Mouritsen (professor of neurosensory science at the University of Oldenberg in Germany – and among other things also a keen wildlife photographer, I learned from his website), and learn more about his research group, which is concerned with animal navigation, here. (My favourite paper title from their list? “Waved Albatrosses can navigate with strong magnets attached to their head” – refreshingly straight and to the point, isn’t it?)
Does anyone reading know more about this topic? It’s very interesting, and I’d like to know more – are there any other known examples of this sort? What’s the nature of biological molecules that are magnetic field sensitive – how do they do it and how is the information interfaced with the rest of the biological system normally?
All so interesting…. And imagine what the bird could see if it “flew” around the sun or around Jupiter…
-cvj
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As ever, you are at the leading edge with the amazing bio-facts. That birds can, perhaps, visually encode a magnetic field, sensed via fragments of the lode-stone of the ancients (though the fact that pigeons had chunks of the stuff in their heads is something I have come across before) is astonishing, and at the same time, getting frighteningly close to Brian Cox (physicist rather than actor with an amazing voice)’s scientific background to Heroes, which is currently being screened in the UK.
A Dangerous Idea?
Hi Clifford,
thank you for the pointer. That’s a fascinating topic indeed! By the way, from reports here in Germany (and at news@nature I’ve learned that the orignal paper is open-access at PLoS One (DOI: 10.1371/journal.pone.0000937, direct link here.).
I don’t know more about this specific results on “magnetic vision” than from the news reports, but the work of the Oldenburg group goes back to research of biologists at “my” University in Frankfurt am Main.
And a different ascpect of these investigations on magnetoreception in migrating brids that is boosting these days is the investigation of this sense in pigeons. Pigeons have in their beak ferromagnetic crystallites of the iron oxides magnetite and maghemite, and this is thought to be important for their reception of magnetic fields, which could help to explain their navigational skills – see e.g. “Homing pigeons can use magnetic cues for locating food.” by Peter Thalau, Elke Holtkamp-Rötzler, Gerta Fleissner and Wolfgang Wiltschko (Naturwissenschaften 94 (2007) 813; DOI: 10.1007/s00114-007-0259-6) and “A novel concept of Fe-mineral-based magnetoreception: histological and physicochemical data from the upper beak of homing pigeons.” by Gerta Fleissner, Branko Stahl, Peter Thalau, Gerald Falkenberg and Günther Fleissner (Naturwissenschaften 94 (2007) 631; DOI: 10.1007/s00114-007-0236-0).
The physical mechanism that may be at work in the pigeons’ beaks is investigated by physicists at the FIAS – including my senior advisor! Two recent papers by them are “Theoretical Analysis of an Iron Mineral-Based Magnetoreceptor Model in Birds” (Ilia A. Solov’yov and Walter Greiner, Biophysical Journal 93 (2007) 1493; DOI: 10.1529/biophysj.107.105098) and and the arxiv “Towards understanding of birds magnetoreceptor mechanism” (arXiv:0704.1763v1).
All this is really fascinating!
Best regards, Stefan
It’s hard to weave a comprehensive view about “magnetic vision” in such a “small post box.” So it may seem “irrelevant” but it’s not.
Sight (and smell et cetera) receptors are quite versatile, and it makes sense that animals evolved to tie in sensory information that way. It is quite easy, IIRC recently they transfered a gene for a new type of rhodopsin to mice and they adopted the new part of the color spectra.
Some species have 4 or more types of photo receptors. (Also, there are women who can have 4 due to a mutation on an X-chromosome.) This adds resolution and seeing into the UV spectra. White flowers have different colors for pollinating insects.
Likewise insects may see polarized light, an additional experience of information that may resemble the overlay from magnetic receptors. As many people have an accidental ability to perceive it too, we can get a sense for how it feels without having to use computer overlays.
That’s interesting information Tony.
Rupert Sheldrake has had similar thoughts on this topic.
Many of academics might have steered clear because of the the thoughts and subject he has about this? It seems to me that if this information is credible then some of Rupert’s work has some substance to it and hence, brings some credibility to the academic outlook.
[…snip…longer remarks cut out… sorry…too long for so far off-topic. -cvj….]
Thorsten Ritz (physics prof at UC Irvine) has done a lot of interesting work along these lines. Perhaps you can entice him up for a talk.
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A few references that I hope might be relevant:
According to an article by Charles Walcott, et al; “Pigeons Have Magnets,” Science, 205:1027, 1979, “… Homing pigeons seem to possess at least two direction sensors. Years of experiments with released birds have proved that they use sun compasses on sunny days but have magnetic backups for cloudy days. But how do they sense the earth’s magnetic field? Paired-coil tests suggested that the pigeon compass resided in the neck or back of the head. Narrowing the search with sensitive magnetometers and two dozen dissected pigeons, the authors discovered tiny bits of tissue containing magnetite crystals. The same tissues contained yellow crystals likely made by the iron-storage protein ferritin, which was probably used in the biological synthesis of the magnetite. …”.
In Science Frontiers #9, Winter 1979, William R. Corliss added the comment: “Many species of mud bacteria also synthesize magnetite for purposes of orientation, indicating that nature or some directive force used the same strategy in two widely separated species.”
Jon Dobson and Tim St. Pierre at the University of Western Australia have a web page at http://www.biophysics.uwa.edu.au/magnetite.html that says: “… Biomineralization of ferrimagnetic magnetite is known to occur in a number of organisms including animals … Recent investigations have revealed the presence of biogenic magnetite in human brain tissue as well … we are examining tissue samples using scanning and transmission electron microscopy (SEM and TEM), electron energy loss spectroscopy (EELS) and energy filter TEM (EFTEM) imaging in order to locate the particles in the tissue and determine their relationships to structures in the brain. The presence of ferrimagnetic material in human brain tissue also provides plausible theoretical mechanisms for the interaction of environmental magnetic fields with the human central nervous system …”.
Kobayashi, Kirschvink, and Nesson, in Nature v.374, p.123, 9 March 1995, say “… A simple calculation shows that the mechanical energy present in a single 0.1 um magnetite crystal exposed to a 60 Hz, 0.1 mT magnetic field is many times the thermal background noise. Such particles, if adsorbed on cell surfaces or ingested by the cells, could conceivably transfer this energy to contiguous cell structures such as mechanically-activated ion channels (which operate with a gating force close to the thermal noise limit), and thereby alter cytoplasmic ion concentrations …”.
Tony Smith
This is interesting! My sister is currently doing grad school in evolutionary biology studying birds in Australia and I’ll have to send it on to her. (Snail-mail though- she’s in one of the very few parts of the world where it’s quicker to write actual letters.) I actually discussed birds and magnetic fields with her while she was looking for a thesis topic… for awhile, she was trying to see if bird mating sites changed based on magnetic fields, but had to abandon that due to some technical limitations.