Characterizing Magnetic Alignment Orientation in Drosophila melanogaster
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1
Virginia Tech, Biological Sciences, United States
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2
Mount Olive College, United States
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3
Virginia Tech, United States
Behavioral studies from all five major classes of vertebrates, as well as several classes of invertebrates, provide evidence for the use of an internal compass sensitive to Earth-strength magnetic fields. Although the integration of magnetic information appears fundamental to a range of behaviors, the sensory receptors, and the biophysical and molecular mechanisms underlying these responses remain unclear. However, evidence from birds, amphibians, and insects suggest that some of these behaviors might be mediated by a light-dependent magnetic compass involving a magnetically sensitive, photo-excited reaction occurring within specialized photoreceptors. The magnetic field is thought to affect the response of photoreceptors containing an ordered array of a specialized photopigments that form long-lived radical pair intermediates in certain alignments relative to an external magnetic field. In some animals this may produce an axially symmetrical, visual pattern superimposed on the animal’s field of view that is fixed with respect to magnetic north.
In addition to magnetic compass orientation, spontaneous or ‘innate’ alignment preferences have been documented in a variety of vertebrate and invertebrate groups. Experimental evidence from insects shows that alignment orientation is mediated by magnetic cues. However, as with magnetic compass responses, the underlying mechanisms and sensory receptors remain elusive. Furthermore, the adaptive significance of spontaneous magnetic alignment behavior is not well understood.
Here we provide evidence for spontaneous quadramodal alignment responses in three strains of Drosophila melanogaster 2nd instar larvae along the 45°, or ‘anti-cardinal’ compass axes (i.e. 45°, 135°, 225°, and 315°). Double-blind experiments in which the magnetic field was present or cancelled confirm that these behaviors are mediated by magnetic cues. Additional experiments characterizing the effect of light on the alignment behaviors reveal that larvae exhibit a wavelength-dependent shift in alignment under 365 nm short- and 490 nm long-wavelength light. Taken together, these data provide compelling evidence that spontaneous alignment preferences exhibited by Drosophila larvae are mediated by a light-dependent magnetic mechanism. Furthermore, a reanalysis of data from a previous study of adult Drosophila found that light-dependent magnetic compass orientation of adults trained along the East or West axis exhibited a 90° splitting around the trained direction, consistent with the quadramodal alignment preferences reported in Drosophila larvae, and may suggest that a common underlying magnetic mechanism mediates both adult and larval behavioral responses. Experiments are currently underway to obtain a detailed spectral dependence curve for the quadramodal alignment response of 2nd instar Drosophila melanogaster that will shed light on the biophysical mechanisms underlying magnetic responses exhibited by a diverse range of organisms.
References
Dommer, D., Gazallo, P., Painter, M. & J. Phillips 2008. Magnetic compass orientation by larval Drosophila melanogaster. J. Insect Physiol. 54: 719-726. (DOI: 10.1016/j.jinsphys.2007.02.001) PMID: 18359039
Phillips, J.B. & O. Sayeed 1993. Wavelength-dependent effects of light on magnetic compass orientation in Drosophila melanogaster. J. Comp. Physiol. 172: 303-308.
Phillips, J.B., R. Muheim & P. E. Jorge 2010b. A behavioral perspective on the biophysics of the light-dependent magnetic compass: a link between directional and spatial perception? J. Exp. Biol. 213: 3247-3255.
Ritz, T., S. Adem & K. Schulten 2000. A model for photoreceptor-based magnetoreception in birds. Biophys. J. 78: 707-718.
Vacha, M., M. Kvicalova, T. Puzova (2009) American cockroaches prefer four cardinal geomagnetic positions at rest. Behaviour. 147: 425-440
Keywords:
Alignment,
Magnetoreception,
navigation,
Orientation
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster Presentation (see alternatives below as well)
Topic:
Orientation and Navigation
Citation:
Painter
M,
Dommer
D,
Altzheizer
W,
Moore
B and
Phillips
JB
(2012). Characterizing Magnetic Alignment Orientation in Drosophila melanogaster.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00360
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Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Mr. Michael Painter, Virginia Tech, Biological Sciences, Blacksburg, VA, 24061, United States, mipainte@vt.edu
Dr. John B Phillips, Virginia Tech, Biological Sciences, Blacksburg, VA, 24061, United States, jphillip@vt.edu