Insecticide Exposure May Pose a Threat to the Future Life Expectancy of Non-Targets: Inferred from Fly Research

The life span of organisms becomes very flexible and vulnerable due to environmental and climatic changes, which have both natural and man-made factors. One such example is the inappropriate use of insecticides and pesticides in the agriculture and health sectors, which cause environmental pollution, despite their agricultural and health benefits. Two of the most widely used organophosphate insecticides, chlorpyrifos (CP) and ethion (ET), are known to have neurotoxic properties and they target to inhibit the neurotransmitter function of acetylcholinesterase (AChE) in insects. Previous studies have shown that exposure to these insecticides brings detrimental health effects to non-targets including humans. The present work aims to estimate the effects of CP and ET on lifespan in two sibling species of Drosophila, Drosophila melanogaster and Drosophila simulans, after being exposed for 24 and 48 hrs to their sublethal concentrations (determined from LC₅₀ and LC₉₀). To understand the molecular mechanism behind this, Differential Expression Gene (DEG) analysis of ET-exposed Drosophila flies was carried out through whole transcriptome sequencing, which shows 85 upregulated and 95 downregulated ageing-associated genes, involved in the regulation of cell cycle, growth and development. The flies were then continuously cultured in insecticide-treated and untreated media (Control) for ten generations, after which the lifespan was calculated (Control vs F₁ vs. F₁₀). In comparison, the results revealed a remarkable reduction of lifespan in F₁ treated, which increased in F₁₀ treated flies, but still, it did not reach up to the average lifespan of the control. Thus, the long-term effect of insecticide exposure on the lifespan of non-targets cannot be overlooked and needs to be further addressed.