THE EFFECT OF SOME ANIONS AND CATIONS UPON THE FLUXES AND NET UPTAKE OF SODIUM IN THE LARVA OF AUEDES AEGYPTI (L).

Abstract

ABSTRACT Starved 4th-instar larvae of Aëdes aegypti, when put into deionized water at a density of ten larvae/zoml., are able to achieve sodium balance at the low external concentration of 5µM Na/1. The balancing process involves a 10% drop in total sodium content, a more or less complete activation of the mechanism for sodium transport, and a reduction in the permeability of the larva to sodium as measured by the net sodium loss into deionized water. It is very probable that most of this reduction occurs in the anal papillae. The relationship between external sodium concentration and sodium influx in larvae previously ‘balanced’ in deionized water is described approximately by the Michaelis equation. The sodium outflux also increases with increasing external sodium concentrations. The net uptake of sodium by ‘balanced larvae’ appears to be significantly greater from solutions of NaCl than from solutions of NaNO3, NaHCO3, and NajSO22. The ions K+ Ca++ Mg++ and NH224 when present as chlorides stimulate the influx of sodium from o-i mM/1. sodium chloride. When present as nitrates or sulphates they either have no effect or cause an inhibition of influx. The results in 4 and 5 suggest that movements of chloride may be important in sodium uptake, and chloride uptake has been found to occur independently of sodium uptake. Measurements of potential difference between haemolymph and medium demonstrate active transport of both sodium and chloride.