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First published online August 31, 2007
Journal of Experimental Biology 210, 3171-3178 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.007567
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Light-dependent magnetoreception: quantum catches and opponency mechanisms of possible photosensitive molecules

Sönke Johnsen1,*, Erin Mattern2 and Thorsten Ritz2

1 Biology Department, Duke University, Durham, NC 27708, USA
2 Physics Department, University of California, Irvine, CA 92697, USA


Figure 1
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  		Fig. 1. Receptor curves used in study. For clarity, all are normalized so that the integral under each curve is identical.

 

Figure 2
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  		Fig. 2. The irradiance spectra under which birds were tested for magnetoreception behavior. All spectra are taken from data given in the studies shown in Table 1.

 

Figure 3
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  		Fig. 3. Irradiance spectra of the single-LED conditions under which birds were tested. Values denote central wavelength; error bars denote the range over which intensity is at least half of that at the peak.

 

Figure 4
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  		Fig. 4. Quantum catch of the various receptors grouped by magnetoreception behavior. Since one cannot compare the catches of the different receptors for reasons described in the text (with the exception of the cone pigments), the catches are normalized by their maximum value for clarity. Values are means ± s.e.m. *P<0.05.

 

Figure 5
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  		Fig. 5. Four possible cone opponency mechanisms plotted against total quantum catch for the receptors involved. (A) LW–MW, (B) MW–SW, (C) LW–SW, (D) LW–(MW+SW). The broken lines show the irradiance spectra during sunset. The black circles denote the conditions when the sun is at the horizon; open circles, solar elevations that are not sunset. The other points are for conditions separated by approximately 1° of solar elevation. Filled symbols, European robin; open symbols, other birds (see Table 1).

 

Figure 6
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  		Fig. 6. A possible opponency mechanism involving gwCry1a and semiquinone. See Fig. 5 for further details.

 

Figure 7
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  		Fig. 7. Likely photocycle of crypotochrome in birds. Light can be absorbed either by the fully oxidized or semiquinone form of flavin, the active chromophore in cryptochrome. Magnetic field effects can, in principle, occur on the reduction from activated flavin (FAD*) to the semiquinone, or on the reoxidation from fully reduced FADH– to fully oxidized FAD.

 




© The Company of Biologists Ltd 2007