Studies on the Exchange and Regulation of Sodium in the Larva of Aedes Aegypti (L.)
1. The net transport of sodium into the haemolymph by sodium-deficient 4th-instar larvae of Aëdes aegypti (L.) has been studied by means of flame photometry. The fluxes associated with this net transport have been studied by means of 22Na. 2. The net transport is much more rapid in fed larvae (rate about 50 mM./l./hr.) than in starved larvae (rate about 10 mM./l./hr.). The fluxes are also much greater in the fed larvae. 3. The fluxes associated with net transport in fed and starved larvae are much greater (initially at any rate) than the fluxes occurring in normal fed and starved larvae during steady-state exchange. 4. In both fed and starved larvae almost all the net transport and the fluxes associated with it occur through the anal papillae, so these organs must be responsible for almost all the difference between fed and starved larvae in the rate of net transport and fluxes. 5. Cytological changes in the anal papillae following upon feeding and starvation are described. 6. The results are discussed in terms of possible carrier mechanisms in the anal papillae.