Turnover of radiosodium in Drosophila melanogaster adults of different ages

The rate of loss of radioactivity from adults of Drosophila melanogaster was observed both in groups and in individual flies of different initial ages up to 1176 hours and maintained at 25°C. Flies were labelled either by rearing them from the egg stage on media containing Na²² or by feeding adults Na²² in the food media. Even though sufficient equilibration time on the media was allowed and the flies were not anaesthetized after once becoming labelled great variation was found in biologic half-life for flies of all ages. A small but significant association of turnover rate with age was found for the males only. The half-life decreased by 1·8 hr for each 100 hr of age. The difference between the mean half-life values for males (81·26 hr) and females (98·24 hr) of all ages combined was statistically significant. The turnover of body sodium for a 24 hr period was 15·5 per cent and 18·5 per cent for females and males respectively.