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The spontaneous locomotor activity of young, middle-aged and old Drosophila melanogaster of both sexes has been videorecorded during three parabolic flights separated by one-day intervals. Fast shifts between 0 g, 1 g and 1.8 g phases are obtained during parabolic flights. Results showed that the activity scores were higher at 0 g during the first flight, but that this effect of microgravity was erased during the two next flights. It may be concluded that flies showed a transient form of reactivity to a new environment, i.e, to repeated rapid variations of gravity levels.

1. Drosophila melanogaster flies have been used in studies of the effects of hypergravity (HG) on aging and longevity. 2. There is no clear longevity decrease with the gravity level up to 4 g and, even at 7 g, flies still live for roughly 40 days. 3. The HG-related changes in fecundity suggest that flies counteract an increased metabolic demand. 4. Viability is barely affected in HG. 5. These results show that flies remain able to lay viable eggs and to five for a fairly long life, even at high HG levels. 6. The study of three behavioral traits affected by aging (climbing activity, pattern of movement, spontaneous locomotor activity) suggests that flies age faster in HG, while no HG effect is clearly detected at young age. 7. These results are observed at HG levels where longevity is not yet affected. 8. Results are discussed in relation with Pearl's rate of living theory (1928).

Longevity of mated and virgin Drosophila melanogaster flies was observed at various gravity levels (1-7.38 g). A slight longevity decrease was observed in the 1-5.14 g range for virgin males, and a larger one in the 5.14-7.38 g range. The effect of gravity was larger for females in the 1-5.14 g range, and at the highest gravity level, bot hsexes had roughly the same longevity, which however remained high (around 40 days). The longevity of mated flies was lower than that of virgins at 1 g, and only a slight longevity decrease was observed in the 1-7.38 g range in females, this decrease being larger for males. Hypergravity appears to have no dragmatic effects on life span and to be of lower importance than the simple effect of mating. This study confirms previous results obtained in the 1-5.02 g range with virgin flies (Le Bourg and Lints. 1989).

Drosophila melanogaster flies climb up the sides of their vial after having been submitted to a mechanical stimulation; that ability is impaired at older ages. The climbing activity (CLI) of flies kept at various gravity levels (1, 3 and 5 g) has been measured throughout life, in cross-sectional studies. Hypergravity had no effect on CLI at young age, but older flies kept in hypergravity displayed lower scores than flies kept at 1 g. Results are discussed in relation with the hypothesis of increased aging rate in hypergravity.

The paths of young, middle-aged and old Drosophila melanogaster flies, kept at various gravity levels (1-5 g) throughout life, have been recorded in a cross-sectional study. Aging flies exhibit more sinuous paths and do not move as far away from their release point as younger ones. These age-related changes in the patterns of movement are expressed at younger ages in flies submitted to hypergravity. As for the climbing activity experiment, the patterns of movement do not clearly vary with the gravity level at young age. Results are discussed in relation to the hypothesis of increased aging rate in hypergravity.

The spontaneous locomotor activity (SLA) of Drosophila melanogaster flies kept at various gravity levels (1-5 g) was recorded in both longitudinal and cross-sectional experiments. No gravity level effect could be detected in the longitudinal one, probably because these flies were allowed (for technical reasons) to rest at 1 g for 15% of their life. By contrast, flies kept at 5 g in the cross-sectional experiment had lower SLA scores at middle and old age than both 1 and 3 g-kept flies. The results of this series of experiments on hypergravity (HG) effects on three forms of locomotor activity (climbing activity, patterns of movement and SLA) allow to conclude that aging is accelerated in HG, even if no longevity decrease could be detected in the 1-4 g range.