Effect of magnetically simulated zero-gravity and enhanced gravity on the walk of the common fruitfly

Richard J A Hill,Camelia E Dijkstra,F Javier Medina,Roberto Marco,Emilio De Juan,Ana I Manzano,Paul Anthony,Raul Herranz,Michael R Davey,Laurence Eaves,Oliver J Larkin

doi:10.1098/rsif.2011.0715

Abstract

Understanding the effects of gravity on biological organisms is vital to the success of future space missions. Previous studies in Earth orbit have shown that the common fruitfly (Drosophila melanogaster) walks more quickly and more frequently in microgravity, compared with its motion on Earth. However, flight preparation procedures and forces endured on launch made it difficult to implement on the Earth's surface a control that exposed flies to the same sequence of major physical and environmental changes. To address the uncertainties concerning these behavioural anomalies, we have studied the walking paths of D. melanogaster in a pseudo-weightless environment (0g*) in our Earth-based laboratory. We used a strong magnetic field, produced by a superconducting solenoid, to induce a diamagnetic force on the flies that balanced the force of gravity. Simultaneously, two other groups of flies were exposed to a pseudo-hypergravity environment (2g*) and a normal gravity environment (1g*) within the spatially varying field. The flies had a larger mean speed in 0g* than in 1g*, and smaller in 2g*. The mean square distance travelled by the flies grew more rapidly with time in 0g* than in 1g*, and slower in 2g*. We observed no other clear effects of the magnetic field, up to 16.5 T, on the walks of the flies. We compare the effect of diamagnetically simulated weightlessness with that of weightlessness in an orbiting spacecraft, and identify the cause of the anomalous behaviour as the altered effective gravity.

Highlights

Life has evolved under the gravitational field of Earth since it began; so it is fascinating and fundamental to find out how living things respond to an environment with different gravity
A primary aim of our experiments is to demonstrate the usefulness of diamagnetic levitation as a viable alternative to more established ground-based techniques for simulating the effects of microgravity on a complex organism, such as the random positioning machine, or parabolic flights
These results corroborate the findings from the experiments performed aboard the Columbia Space Shuttle and the ISS that fruitflies walk more quickly in the microgravity environment and are ‘active’ more frequently

Summary

Introduction

Life has evolved under the gravitational field of Earth since it began; so it is fascinating and fundamental to find out how living things respond to an environment with different gravity. Drosophila melanogaster is an ideal model organism on which to study the effects of gravity: the flies are small enough that many individuals can be contained in compact cells suitable for space-flight, yet complex enough to possess a sophisticated gravity sense mechanism [3]. Their use is ubiquitous in studies of biological developmental processes and in endeavours to understand cellular mechanisms in higher organisms, and they have been used in a number of studies on the origin of the biological gravity sense mechanism [4,5]. The motility of these flies has been linked to molecular ageing responses that could be of significance for future human space exploration [6]

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Conclusion