OSMOTIC EFFECTS AS A FACTOR MODIFYING INSECTICIDE TOXICITY ON AEDES AND ARTEMIA

Euryhaline species are more tolerant of various insecticides under iso smotic conditions. Two euryhaline species, Aedes taeniorhynchus (Wiede mann) and Artemia sp., were exposed to four insecticides (aldicarb, di methoate, imidacloprid, tebufenozide), under isosmotic and hyperosmoti c conditions. Mortality under these two osmotic conditions was observe d and compared to evaluate salinity as a contributing factor to insect icide toxicity. Artemia was more tolerant of all chemicals tested than A. taeniorhynchus under isosmotic conditions based on the percentage mortality observed. Mortality of Artemia under isosmotic conditions wa s dependent on the length of exposure; A. taeniorhynchus did not exhib it time dependence. Less mortality was observed in populations of both test species under isosmotic conditions compared with hyperosmotic co nditions. However, the variation in mortality due to exposure to test chemicals was of greater magnitude in A. taeniorhynchus than Artemia. This result indicates that higher salinity is a greater stress on A. t aeniorhynchus than Artemia when exposed to the test insecticides at th e concentration ranges tested in this study. (C) 1998 Academic Press.