title: Magnetoreception in birds: II. Behavioural experiments concerning the cryptochrome cycle.
abstract: Behavioural tests of the magnetic compass of birds and corresponding immunohistological studies on the activation of retinal cryptochrome 1a, the putative receptor molecule, showed oriented behaviour and activated Cry1a under 373 nm UV, 424 nm blue, 502 nm turquoise and 565 nm green light, although the last wavelength does not allow the first step of photoreduction of cryptochrome to the semiquinone form. The tested birds had been kept under 'white' light before, hence we suggested that there was a supply of semiquinone present at the beginning of the exposure to green light that could be further reduced and then re-oxidized. To test the hypothesis in behavioural experiments, we tested robins, Erithacus rubecula, under various wavelengths (1) after 1 h pre-exposure to total darkness and (2) after 1 h pre-exposure to the same light as used in the test. The birds were oriented under blue and turquoise light, where the full cryptochrome cycle can run, but not under green light. This finding is in agreement with the hypothesis. Orientation under green light appears to be a transient phenomenon until the supply of semiquinone is depleted.
authors.affiliation: Goethe-Universität Frankfurt, FB Biowissenschaften, Max-von-Laue-Straße 13, D-60438 Frankfurt am Main, Germany Wiltschko@bio.uni-frankfurt.de.
authors.forename: Roswitha
authors.initials: R
authors.lastname: Wiltschko
authors.affiliation: Goethe-Universität Frankfurt, FB Biowissenschaften, Max-von-Laue-Straße 13, D-60438 Frankfurt am Main, Germany.
authors.forename: Dennis
authors.initials: D
authors.lastname: Gehring
authors.affiliation: Goethe-Universität Frankfurt, FB Biowissenschaften, Max-von-Laue-Straße 13, D-60438 Frankfurt am Main, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Denzau
authors.affiliation: Goethe-Universität Frankfurt, FB Biowissenschaften, Max-von-Laue-Straße 13, D-60438 Frankfurt am Main, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Nießner
authors.affiliation: Goethe-Universität Frankfurt, FB Biowissenschaften, Max-von-Laue-Straße 13, D-60438 Frankfurt am Main, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wiltschko
mesh_terms: D025041:Animal Migration / Q000502:physiology; D000818:Animals; D056931:Cryptochromes / Q000737:chemistry* / Q000528:radiation effects; D008027:Light; D060526:Magnetic Fields; D009949:Orientation / Q000502:physiology*; D010084:Oxidation-Reduction; D020308:Songbirds; D014466:Ultraviolet Rays
chemical_list: D056931:Cryptochromes
keywords: Activated Cry1a; Cryptochrome 1a; Flavin cycle; Migratory orientation; Photoreduction; Radical pair mechanism