Abstract
BackgroundAppropriate vertical movement is critical for the survival of flying animals. Although negative geotaxis (moving away from Earth) driven by gravity has been extensively studied, much less is understood concerning a static regulatory mechanism for inducing positive geotaxis (moving toward Earth).ResultsUsing Drosophila melanogaster as a model organism, we showed that geomagnetic field (GMF) induces positive geotaxis and antagonizes negative gravitaxis. Remarkably, GMF acts as a sensory cue for an appetite-driven associative learning behavior through the GMF-induced positive geotaxis. This GMF-induced positive geotaxis requires the three geotaxis genes, such as cry, pyx and pdf, and the corresponding neurons residing in Johnston’s organ of the fly’s antennae.ConclusionsThese findings provide a novel concept with the neurogenetic basis on the regulation of vertical movement by GMF in the flying animals.Electronic supplementary materialThe online version of this article (doi:10.1186/s13041-016-0235-1) contains supplementary material, which is available to authorized users.
Highlights
Appropriate vertical movement is critical for the survival of flying animals
Potentiated negative geotaxis by near-zero geomagnetic field (GMF) To determine if GMF influences the geotactic behaviors of Drosophila, we constructed a GMF condition ranging from near-zero to ca. 85 μT which is comparable to the ambient GMF on Earth using a Helmholtz coil system (Fig. 1a)
We attempted to modulate the intensity of GMF to a near-zero condition (Additional file 1: Table S1), and the tube-positioning assay, a modified version of the tube-climbing assay, was performed in the test cube to measure vertical positioning of flies at Zeitgeber time (ZT) 5 to ZT8 (Fig. 1b and Additional file 2: Figure S1A)
Summary
Appropriate vertical movement is critical for the survival of flying animals. negative geotaxis (moving away from Earth) driven by gravity has been extensively studied, much less is understood concerning a static regulatory mechanism for inducing positive geotaxis (moving toward Earth). Geotaxis is a typical innate behavioral response of all living organisms characterized by locomotive activities toward or away from Earth. It is generally accepted that microgravity in a space craft or simulated microgravity on the ground provides suitable experimental conditions to investigate whether gravity provokes geotaxis of living organisms [9,10,11]. This consensus may be flawed because geotactic behaviors under these conditions are confounded by a wide range of artifacts. GMF provides migratory animals an important behavioral cue for their horizontal migration [14, 15]. Because the trajectories of such flying or swimming animals occur not in
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