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Sensing magnetic directions in birds: radical pair processes involving cryptochrome.

Wiltschko R, Wiltschko W - Biosensors (Basel) (2014)

Bottom Line: Cryptochromes have been suggested as receptor molecules.Cry1a is found in the eyes of birds, where it is located at the membranes of the disks in the outer segments of the UV-cones in chickens and robins.Immuno-histochemical studies show that it is activated by the wavelengths of light that allow magnetic compass orientation in birds.

View Article: PubMed Central - PubMed

Affiliation: Fachbereich Biowissenschaften, J.W. Goethe-Universität Frankfurt, Max von Laue Straße 13, D-60438 Frankfurt am Main, Germany; E-Mail: wiltschko@zoology.uni-frankfurt.de.

ABSTRACT
Birds can use the geomagnetic field for compass orientation. Behavioral experiments, mostly with migrating passerines, revealed three characteristics of the avian magnetic compass: (1) it works spontaneously only in a narrow functional window around the intensity of the ambient magnetic field, but can adapt to other intensities, (2) it is an "inclination compass", not based on the polarity of the magnetic field, but the axial course of the field lines, and (3) it requires short-wavelength light from UV to 565 nm Green. The Radical Pair-Model of magnetoreception can explain these properties by proposing spin-chemical processes in photopigments as underlying mechanism. Applying radio frequency fields, a diagnostic tool for radical pair processes, supports an involvement of a radical pair mechanism in avian magnetoreception: added to the geomagnetic field, they disrupted orientation, presumably by interfering with the receptive processes. Cryptochromes have been suggested as receptor molecules. Cry1a is found in the eyes of birds, where it is located at the membranes of the disks in the outer segments of the UV-cones in chickens and robins. Immuno-histochemical studies show that it is activated by the wavelengths of light that allow magnetic compass orientation in birds.

No MeSH data available.


Testing robins with radio frequency fields of 7 MHz, 470 nT, added in different alignments with respect to the vector of the local geomagnetic field. (a) Control: geomagnetic field only; (b) radio frequency field added parallel to the magnetic vector, that is 24° to the downward direction; (c) added vertically, 24° to the magnetic vector; (d) added 48° to the magnetic vector, which means 24° to the downward direction—Symbols as in Figure 1b (data from [44]).
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biosensors-04-00221-f006: Testing robins with radio frequency fields of 7 MHz, 470 nT, added in different alignments with respect to the vector of the local geomagnetic field. (a) Control: geomagnetic field only; (b) radio frequency field added parallel to the magnetic vector, that is 24° to the downward direction; (c) added vertically, 24° to the magnetic vector; (d) added 48° to the magnetic vector, which means 24° to the downward direction—Symbols as in Figure 1b (data from [44]).

Mentions: A diagnostic test for an involvement of radical pair processes is to apply radio frequency fields in the MHz (MegaHertz)-range, as they would interfere with the singlet-triplet interconversion [41,42]. Here, the alignment of the applied oscillating field with respect to the vector of the static background field is important [43]. In critical tests, the radio frequency fields were therefore added in different alignments to the local geomagnetic field with its inclination of 66°. A 1.315 MHz and a 7 MHz field of 470 nT, added parallel, did not disrupt orientation, but when the same fields were applied vertically, i.e., at an angle of 24° to the vector of the geomagnetic field, or at an angle of 48°, the birds were disoriented, indicating that they lacked meaningful directional information (Figure 6) [44,45]. These findings support the Radical Pair Model of magnetoreception.


Sensing magnetic directions in birds: radical pair processes involving cryptochrome.

Wiltschko R, Wiltschko W - Biosensors (Basel) (2014)

Testing robins with radio frequency fields of 7 MHz, 470 nT, added in different alignments with respect to the vector of the local geomagnetic field. (a) Control: geomagnetic field only; (b) radio frequency field added parallel to the magnetic vector, that is 24° to the downward direction; (c) added vertically, 24° to the magnetic vector; (d) added 48° to the magnetic vector, which means 24° to the downward direction—Symbols as in Figure 1b (data from [44]).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4264356&req=5

biosensors-04-00221-f006: Testing robins with radio frequency fields of 7 MHz, 470 nT, added in different alignments with respect to the vector of the local geomagnetic field. (a) Control: geomagnetic field only; (b) radio frequency field added parallel to the magnetic vector, that is 24° to the downward direction; (c) added vertically, 24° to the magnetic vector; (d) added 48° to the magnetic vector, which means 24° to the downward direction—Symbols as in Figure 1b (data from [44]).
Mentions: A diagnostic test for an involvement of radical pair processes is to apply radio frequency fields in the MHz (MegaHertz)-range, as they would interfere with the singlet-triplet interconversion [41,42]. Here, the alignment of the applied oscillating field with respect to the vector of the static background field is important [43]. In critical tests, the radio frequency fields were therefore added in different alignments to the local geomagnetic field with its inclination of 66°. A 1.315 MHz and a 7 MHz field of 470 nT, added parallel, did not disrupt orientation, but when the same fields were applied vertically, i.e., at an angle of 24° to the vector of the geomagnetic field, or at an angle of 48°, the birds were disoriented, indicating that they lacked meaningful directional information (Figure 6) [44,45]. These findings support the Radical Pair Model of magnetoreception.

Bottom Line: Cryptochromes have been suggested as receptor molecules.Cry1a is found in the eyes of birds, where it is located at the membranes of the disks in the outer segments of the UV-cones in chickens and robins.Immuno-histochemical studies show that it is activated by the wavelengths of light that allow magnetic compass orientation in birds.

View Article: PubMed Central - PubMed

Affiliation: Fachbereich Biowissenschaften, J.W. Goethe-Universität Frankfurt, Max von Laue Straße 13, D-60438 Frankfurt am Main, Germany; E-Mail: wiltschko@zoology.uni-frankfurt.de.

ABSTRACT
Birds can use the geomagnetic field for compass orientation. Behavioral experiments, mostly with migrating passerines, revealed three characteristics of the avian magnetic compass: (1) it works spontaneously only in a narrow functional window around the intensity of the ambient magnetic field, but can adapt to other intensities, (2) it is an "inclination compass", not based on the polarity of the magnetic field, but the axial course of the field lines, and (3) it requires short-wavelength light from UV to 565 nm Green. The Radical Pair-Model of magnetoreception can explain these properties by proposing spin-chemical processes in photopigments as underlying mechanism. Applying radio frequency fields, a diagnostic tool for radical pair processes, supports an involvement of a radical pair mechanism in avian magnetoreception: added to the geomagnetic field, they disrupted orientation, presumably by interfering with the receptive processes. Cryptochromes have been suggested as receptor molecules. Cry1a is found in the eyes of birds, where it is located at the membranes of the disks in the outer segments of the UV-cones in chickens and robins. Immuno-histochemical studies show that it is activated by the wavelengths of light that allow magnetic compass orientation in birds.

No MeSH data available.