A Biomonitoring Procedure Utilizing Negative Phototaxis of First

24061 Abstract. Negative phototaxis of newly hatched Aedes aegypti L. larvae was inhibited by exposure to three heavy metals and five organic insecticides. This response was quantified in an inexpensive multiunit apparatus consisting of four glass troughs perpendicular to a uniform light source. The criterion of toxic effect, established with cupric sulfate as a standard, was: inability of larvae to migrate 30 cm in 60 sec after 8 hr of pre-exposure, designated as 8-hr ECso. The photomigration procedure was more sensitive than our compara- tive 24-hr acute lethal toxicity tests on metals. The 8-hr ECso values for cadmium, chromium and copper were 0.6, 2.4, and 1.4 mg/L, respectively. Values for insecticides ranged from 0.003 mg/L for fenitrothion (organophos- phate) to 0.39 mg/L for methomyl (carbamate). Emphasis in water quality management is shifting from a posteriori measurement of incurred damage towards the prevention of unacceptable conditions (Mount 1977). This has produced a need for more rapid assessment of field conditions and in-plant effluent toxicity. Most recent laboratory approaches have empha- sized continuous monitoring using fish or algae as sensors (Calms et al. 1973, 1977). Many of these biological methods require elaborate facilities and substan- tial expenditures of time and money. There is a recognized need for research aimed at development of sensitive, easily performed toxicity tests which are both rapid and economical (Doudoroff 1977). Sublethal changes in behavioral patterns are considered to be among the most sensitive indicators of toxic effect (Davis 1975, Sprague 1971). Performance parameters such as activity, reactivity, and swimming ability, which can be measured quantitatively, have been suggested as the most satisfactory methods of sublethal toxicity testing (Sprague 1971, Wal- lace et al. 1975, Kleerekoper 1977). A characteristic behavioral trait of larval mosquitoes such as Aedes aegypti L. (Diptera) is their intense negative phototaxis. This trait was first studied in bioassay work by Burcb_field et al. (1952) and Burcb_field and Hartzell (1955). They demonstrated that in the presence of toxic materials, larval response was reduced long before death occurred. This principle has since been used in other investigations on insecticidal activity (Das and Needham 1961, Turnipseed and Reed 1963, Beesley 1962, Godin et al. 1965). All of these studies were based on an experimental design involving only one trough or chamber.