ABSTRACT
The osmotic pressure, sodium, potassium and chloride concentrations have been determined in the haemolymph of normal Drosophila melanogaster larvae and of larvae selected to survive on standard medium containing 7% NaCl (‘selected’ larvae).
The haemolymph composition of normal larvae developing on standard medium shows features characteristic of pterygote insects.
The haemolymph of ‘selected’ larvae developing on standard medium containing 7% NaCl is markedly hypotonic to the medium. There is only a small rise in NaCl concentration.
Both normal larvae and ‘selected’ larvae can survive and develop on standard medium containing 7% KCl.
The haemolymph of ‘selected’ larvae developing on standard medium containing 7% KCl is markedly hypotonic to the medium. There is a decreased Na:K ratio and a very markedly increased Cl:organic anion ratio.
The nature of the mechanisms regulating the haemolymph composition is discussed.
