A longitudinal study of the effects of age on spontaneous locomotor activity in Drosophila melanogaster.

The spontaneous locomotor activity of Drosophila melanogaster was observed longitudinally, in both sexes, at young and old age, during a photophase of 12 h. 75 observations of each fly (n = 200 at young age, n = 98 at old age) were made during each photophase. At a populational level and with increasing age the difference between the maximal and minimal percentages of flies active during the photophase diminishes seriously; moreover, the scattering of the observations increases with increasing age. At an individual level females are more active than males at both ages and the scores of activity of both males and females decrease with increasing age. The effects observed, both at the populational and at the individual level, are due solely to age; they are not due to a differential survival depending on or linked to the score of activity exhibited at young age.