The Composition of the Haemolymph of the Larva of Drosophila Melanogaster

Abstract

1. 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). 2. The haemolymph composition of normal larvae developing on standard medium shows features characteristic of pterygote insects. 3. 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. 4. Both normal larvae and ‘selected’ larvae can survive and develop on standard medium containing 7% KCl. 5. 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. 6. The nature of the mechanisms regulating the haemolymph composition is discussed.