Combined effect of Lead acetate and Zinc chloride on the Fitness of Drosophila melanogaster

Heavy metals have been considered as one of the key environmental toxicants with a wide range of health effects on humans. The bulk of information available today is mainly focused on the single toxin studies with only few studies enumerating the synergistic, additive or protective effects of these heavy metals. In current study, Drosophila was used as a model to investigate the effects of two prominent heavy metals- Lead (Pb) and Zinc (Zn). The developmental time, viability and fertility of these fruit flies after a combined and single exposure to lead acetate and/or zinc chloride were assessed with a focused aim of learning if the combined exposure at sub- lethal concentrations provokes synergistic changes in the fitness of Drosophila melanogaster. Larval feeding method was employed throughout the developmental period of the experimental subjects to administer the compounds singly or in combination while maintaining multiple replicates in order to minimize experimental error. Subsequently, number of offspring produced, their eclosion time and viability were recorded. Our results show that developmental exposure of sub lethal concentrations of lead acetate and zinc chloride provokes disturbances in the fitness of flies. A delay in developmental time was shown which is far more pronounced for the combined exposure than single lead intoxication. A synergistic effect was seen on the developmental viability with a survivability of only 10- 28% at combined exposure of zinc and lead. Further in contrast to the prior parameters, combined treatment showed a significant increase in fertility when compared to single exposure of lead acetate- suggesting a protective effect of Zinc over Lead with respect to fertility.