Meeting Abstract

39.3  Thursday, Jan. 5  Characterizing the Light-dependent Magnetic Compass of Drosophila melanogaster PAINTER, M.S.*; DOMMER, D.H.; GNIRKE, M; TRAN, D; MOORE, B; PHILLIPS, J.B.; Virginia Tech mipainte@vt.edu

The use of geomagnetic field cues during orientation, navigation, and homing behavior has been demonstrated in a diverse array of organisms, ranging from bacteria to vertebrates, yet the putative receptors and mechanisms underlying this behavior remain elusive. Both theoretical and empirical evidence from birds, amphibians, and insects suggest these behaviors are mediated by a light-dependent magnetic compass (LDMC) involving a magnetically sensitive biochemical reaction that forms long-lived radical pair intermediates. Cryptochrome’s have been proposed as likely candidates mediating the LDMC, as they are the only animal photoreceptor known to form radical pair intermediates. Furthermore, the wavelength-dependence of the magnetic compass responses in insects and amphibians are consistent with the absorption spectra of the fully reduced and radical forms of the cryptochrome flavin chromophore; the magnetic field’s effect on a photo-equilibrium between these two redox forms has been proposed to underlie the LDMC. Experiments are currently being carried out to obtain a detailed spectral dependence curve for the magnetic compass response of larval Drosophila melanogaster. Larval flies will be tested under monochromatic light varying in wavelength from 370nm to 640nm (at 30nm intervals) of equal light intensity. The spectral dependence of the larval LDMC will be compared to the absorption spectra of the two redox states of DmCry, as well of those of other candidate molecules. Characterizing the magnetic compass used by larval flies will fill critical gaps in our understanding of the biophysical mechanism underlying the light-dependent magnetic compass.