The development of resistance to caffeine in Drosophila prosaltans: productivity and longevity after ten generations of treatment.

The productivity of Drosophila prosaltans treated with six concentrations of caffeine (from 50 micrograms/ml to 2,500 micrograms/ml of culture medium) during ten generations (approximately 8 months) decreased in a dosage dependent manner in every generation, but at the end of the treatment the flies in all experiments recovered normal productivity, except for those treated with 2,500 micrograms/ml. Longevity in the tenth generation was significantly reduced in males and females only in the 2,500 micrograms/ml dosage, with males being much more affected than females. In a previous study in which the treatment was done in a single generation, productivity exhibited only a partial recovery when the treatment ceased and longevity was significantly reduced in 1,500 micrograms/ml dosages. The hypothesis of selection occurring in ten generations leading to recovery in productivity and to a reduction in the processes which cause a decrease in longevity is being considered.