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The study explored variations in the life cycle parameters in Drosophila melanogaster as a function of treatment with fluorinated insecticide, cryolite. Some of the life cycle parameters considered in this study were larval duration, pupal duration, and percentage of adult fly emergence in D. melanogaster of Oregon R strain. Freshly hatched first instar larvae were transferred to different dietary concentrations of the test chemical (5, 10, 15, 20, 40, 60, 80, 100, 150, and 200 ppm). Larval duration, pupal duration, and the emergence of flies of both treated and control groups were recorded. Results obtained show a significant (p < 0.001-0.05) change in the mentioned parameters in the treated flies when compared with the controls. Interestingly, the percentage emergence of flies shows a decreasing trend along with increase in treatment concentration and almost no detectable emergence is observed in 200 ppm treatment category until the 20th day of experiment. Thus, the study indicates insecticide-induced variation in duration of different life stages and thereby suggests an effect of the fluorinated insecticide on the biology of a nontarget organism like Drosophila.

The starting point of toxicity testing of any chemical in an organism is the determination of its Lethal Concentration 50 (LC50). In the present study, LC50 of a fluorinated insecticide cryolite is determined in a non-target insect model, Drosophila melanogaster. Interestingly, the result shows that acute LC50 of cryolite was much greater in comparison to the chronic one in case of Drosophila larvae. Larvae which were exposed to 65,000 to 70,000 µg/ml cryolite through food showed 50% mortality after 18 hours of acute exposure, whereas only 150 to 160 µg/ml cryolite was sufficient to cause 50% mortality in case of chronic exposure. Thus cryolite in a small amount when applied once cannot produce noticeable changes in Drosophila, whereas the same amount when used continuously can be fatal. The non-feeding pupal stage was also seen to be affected by chemical treatment. This suggests that the test chemical affects the developmental fate and results in failure of adult emergence. Absence of chemical-induced mortality in adults assumes that the toxicity of cryolite might be restricted to the preimaginal stages of the organism. Reduction in body size of larvae after ingestion of cryolite (with food) in acute treatment schedule is another interesting finding of this study. Some individuals consuming cryolite containing food cannot survive whereas the few survivors manifest a significant growth retardation which might be due to a tendency of refusal in feeding. Hence the present findings provide a scope of assessment of risk of other similar non-target groups.