The effect of radioactive phosphorus on the growth and development of Culex pipiens molestus Forsk. (Diptera, Culicidae)

Abstract

The use of radioisotopes as tracers for the study of flight ranges of mosquitos has necessitated laboratory studies to ascertain appropriate, safe and efficient methods of utilisation. Preliminary results were published by Hassett & Jenkins (1949) and by Bugher & Taylor (1949) for Aedes aegypti (L.) and for arctic species by . These papers describe early laboratory results and the first field studies for both arctic and tropical species of mosquitos. AbdelMalek & Abdel-Wahab (1961) studied the uptake of 32 P by Culex pipiens molest us Forsk. using an autoradiographic technique. In the course of that study, the senior author noticed some effects on the growth and development of the larvae, pupae and adults which were produced by the radioisotope. Laboratory experiments were therefore carried out to ascertain more precisely the effects of radiophosphorus on G. p. molestus. The present paper is a report on the results of these studies. Materials and methods.Radioactive larvae, pupae and adults of G. p. molestus were produced in the laboratory by putting radioactive phosphorus in the form of Na 2 H 32 PO 4 into the larval rearing medium which consisted of tap water and pellets of dog food. The larvae were reared in 100-ml. beakers. Two series of these beakers, labelled I and II, were used, each consisting of seven beakers containing concentrations of 32 P as listed in Table I. Fifty ml. of each of these concentrations were made and into each vessel were introduced 100 second-stage larvae of G. p. molestus. The laboratory temperature was 17 + 2°C, and the relative humidity 75 + 5 per cent. TABLE I. Concentrations of 32 P used (in microcuries per millilitre per beaker). Beaker S2 P concentration in (ic./ml.A 0 B 0-05 C 0-5 D 1-0 E 3-0 F 5-0 a 10-0From series I, four batches, each of 10 larvae, were removed after 5, 10, 15 and 20-day periods, respectively. The larvae in series II were allowed to reach the adult stage. The larvae removed from series I were killed by being dipped in hot water. They were then washed in three changes of distilled water and then once with 70 per cent, ethyl alcohol before they were stored in 70 per cent, alcohol * Post-doctorate Fellow,