ABSTRACT
Larvae of the freshwater mosquito Aëdes aegypti (L.) are able to maintain their principal electrolytes against a steep concentration gradient between the haemolymph and the external medium. The concentration of monovalent ions such as Na+, K+ and Cl- is kept far above that in the external medium by processes of active transport which are located in the anal papillae, the rectum and the Malpighian tubules (Koch, 1938; Ramsay, 1953; Treherne, 1954; Stobbart, 1959, 1960, 1965, 1967). Ithasbeen demonstrated that over 90 % of the exchange of monovalent ions occurs through the anal papillae (Treherne, 1954), but these organs are not permeable to bivalent ions (Wigglesworth, 1933). The processes which regulate the exchange of bivalent ions between the larva and the external medium have not yet been elucidated. Recently, we have demonstrated that larvae of Aëdes aegypti maintain a saturable transport system for the uptake of calcium ions from dilute calcium solutions (Barkai & Williams, 1983). This system obeyed Michaelis-Menten kinetics and its activity was susceptible to ruthenium-red which selectively inhibits Ca2+-activated ATPase (Watson, Vincenzi & Davis, 1971).
