79.5 Sunday, Jan. 6 Animal Magnetism: applying the methods of visual ecology to a holy grail of sensory biology JOHNSEN, S*; MATTERN, E; RITZ, T; Duke University; Univ. of California, Irvine; Univ. of California, Irvine firstname.lastname@example.org
Dozens of experiments on magnetosensitive, migratory birds have shown that their magnetic orientation behavior depends on the spectrum of light under which they are tested. However, it is not certain whether this is due to a direct effect on the magnetoreceptive system and which photosensitive molecules may be involved. We examined 62 experiments of light-dependent magnetoreception in three crepuscular and nocturnal migrants (48 for the European robin Erithacus rubecula, 10 for the Silvereye Zosterops lateralis, and 4 on the Garden Warbler Sylvia Borin). For each experiment, we calculated the relative quantum catches of seven of the eight known photosensitive molecules found in the eyes of passerine birds: a short (SW), medium (MW), and long wavelength (LW) cone pigment, rhodopsin, melanopsin, and cryptochrome in its fully-oxidized and semiquinone state. The following five opponency processes were also calculated: LW-SW, LW-MW, MW-SW, LW-(MW+SW), and cryptochrome-semiquinone. Two significant inhibitors of magnetoreceptive behavior were overall irradiances (from 400 to 700 nm) higher than those found at sunset and high quantum catch by the LW receptor. The results were also consistent with the hypothesis that high quantum catch by the semiquinone form of cryptochrome inhibits magnetoreception. The opponency mechanism that best separated oriented from non-oriented behavior was LW-MW, where a difference above a certain level inhibited orientation. Certain regions of experimental spectral space have been over-sampled, while large regions have not been sampled at all, including: 1) from 440 to 500 nm at all irradiance levels, 2) for wavelengths longer than 570 nm from 1012 to 3 x 1012 photons/s/cm2, and 3) for wavelengths less than 560 nm from 1012 to 3 x 1012 photons/s/cm2 and below 5 x 1011 photons/s/cm2.