Motility and aging in Drosophila have proven to be highly modified under altered gravity conditions (both in space and ground simulation facilities). In order to find out how closely connected they are, five strains with altered geotactic response or survival rates were selected and exposed to an altered gravity environment of 2g. By analysing the different motile and behavioural patterns and the median survival rates, we show that altered gravity leads to changes in motility, which will have a negative impact on the flies’ survival. Previous results show a differential gene expression between sessile samples and adults and confirm that environmentally-conditioned behavioural patterns constrain flies’ gene expression and life span. Therefore, hypergravity is considered an environmental stress factor and strains that do not respond to this new environment experience an increment in motility, which is the major cause for the observed increased mortality also under microgravity conditions. The neutral-geotaxis selected strain (strain M) showed the most severe phenotype, unable to respond to variations in the gravitational field. Alternatively, the opposite phenotype was observed in positive-geotaxis and long-life selected flies (strains B and L, respectively), suggesting that these populations are less sensitive to alterations in the gravitational load. We conclude that the behavioural response has a greater contribution to aging than the modified energy consumption in altered gravity environments.
Research Containing: Motility
Human exploration of outer space will eventually take place. In preparation for this endeavour, it is important to establish the nature of the biological response to a prolonged exposure to the space environment. In one of the recent Soyuz Missions to serve the International Space Station (ISS), the Spanish Soyuz mission in October 2003, we exposed four groups of Drosophila male imagoes to microgravity during the almost eleven days of the Cervantes mission to study their motility behaviour. The groups were three of young flies and one of mature flies, In previous space experiments, we have shown that when imagoes are exposed to microgravity they markedly change their behaviour by increasing their motility, especially if subjected to these conditions immediately after hatching. The constraints of the current Soyuz flights made it impossible to study the early posthatching period. A low temperature cold transport was incorporated as a possible way out of this constraint. It turned out that on top of the space flight effects, the cold treatment by itself, modifies the motility behaviour of the flies. Although the four groups increased their motility, the young flies did it in a much lower extent than the mature flies that had not been exposed to the low temperature during transportation. Nevertheless, the flies flown in the ISS are still more active than the parallel ground controls. As a consequence of the lower motility stimulation in this experiment, a likely consequence of the cold transport step, no effects on the life spans of the flown flies were detected. Together with previous results, this study confirms that high levels of motility behaviour are necessary to produce significant decreases in fly longevity.