Retinal cryptochrome in a migratory passerine bird: a possible transducer for the avian magnetic compass
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The currently discussed model of magnetoreception in birds proposes that the direction of the magnetic field is perceived by radical-pair processes in specialized photoreceptors, with cryptochromes suggested as potential candidate molecules mediating magnetic compass information. Behavioral studies have shown that magnetic compass orientation takes place in the eye and requires light from the blue-green part of the spectrum. Cryptochromes are known to absorb in the same spectral range. Because of this we searched for cryptochrome (CRY) in the retina of European robins, Erithacus rubecula, passerine birds that migrate at night. Here, we report three individually expressed cryptochromes, eCRY1a, eCRY1b, and eCRY2. While eCRY1a and eCRY2 are similar to the cryptochromes found in the retina of the domestic chicken, eCRY1b has a unique carboxy (C)-terminal. In light of the ‘radical-pair’ model, our findings support a potential role of cryptochromes as transducers for the perception of magnetic compass information in birds.
KeywordsRetina Flight Muscle Magnetic Compass Domestic Chicken Migratory Restlessness
We gratefully acknowledge laboratory support from Stephen L. Dellaporta and Maria A. Moreno of Yale University during the early months of this study. We thank Allen G. Collins for comments on an earlier draft of this manuscript and Agrani Rump for isolating parts of the eCRY2 sequence. Our work was supported by the Deutsche Forschungsgemeinschaft (grants to W.W. and B.S.), the Human Frontier Science Program (grant to B.S.) and the Studienstiftung des Deutschen Volkes (doctoral fellowship to A.M). The study was performed according to the laws and regulations on animal welfare in Germany.
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