WHOLE BODY TURNOVER OF POTASSIUM TRACED BY RADIORUBIDIUM IN ADULT DROSOPHILA (DROSOPHILIDAE) AND MEGASELIA (PHORIDAE)

Adults of Drosophila melanogaster, D. repleta, and Megaselia scalaris were labelled by feeding for 2-5 days on food containing 86Rb. The flies were then divided, without the use of anaesthesia, into samples of known numbers and placed on food containing different concentrations of RbCl, KCl, or NaCl and maintained at 25°C. Rates of loss of 86Rb were determined from frequent measurements of radioactivity in the samples of unanaesthetized flies. Rates of loss of 86Rb in all three species increased progressively with higher concentrations of KCl in the food. The rates were practically identical when RbCl was substituted for KCl. Doubling the concentration of potassium of potassium plus rubidium in the food of each species reduced the biological half-life of 86Rb to about one-fifth. The rates of loss in all three species were little affected by great differences in concentration of NaCl added to the food but were reduced similarly by greatly different additions of NaCl to the food. Significant differences in the biological half-life were found among the three species. The biological half-life in D. repleta was generally five or six times that of D. melanogaster and Megaselia. No significant differences in biological half-life were observed between the sexes of any one of the three species. © 1968.