Ion Concentration and Activity in the Haemolymph of Aedes Aegypti Larvae

Abstract

The ionic composition of the haemolymph was measured in fourth instar larvae of Aedes aegypti (reared in 0.30% sea water, the animals' natural salinity range). Inorganic ions and free amino acids form a substantial part of the haemolymph osmotic concentration. With increasing external osmotic pressure, there is an increase in the concentration of the amino acids, not the major inorganic cations. Measurements with ion-selective electrodes indicate that the activities of sodium, potassium and chloride can vary independently of their total concentration. The osmotic contribution of these inorganic ions is therefore not necessarily determined by their total concentration.