Exposição de risco: contaminação não-seletiva do malation em formigas Odontomachus brunneus (Patton, 1894) (Hymenoptera: formicidae)

Abstract

Insecticides are used in urban areas to eliminate unwanted insects and disease vectors, such as the dengue-transmitting mosquito Aedes aegypti (Linnaeus, 1762), which will be controlled by the insecticide Malathion, a non-selective organophosphate with neurotoxic effects, until 2023. However, its application causes contact with non-target insects, such as urban ants, which play important ecological roles. Thus, the objective of this study was to determine the survival of ants of the species Odontomachus brunneus (Patton, 1894) exposed to Malathion through indirect contact, in addition to evaluating whether there is a preference between environments with and without contamination. A survival bioassay was performed with the following concentrations: 1000 mg/L (T1), 100 mg/L (T2), 10 mg/L (T3) and 1 mg/L (T4), as well as a behavioral bioassay, where the Contaminated Area (CT) used 1000 mg/L of Malathion and the Negative Control (NC) distilled water, evaluating the displacement and self-cleaning of the foragers. The results of the survival analysis demonstrated that the concentrations T1, T2 and T3 are highly toxic, with mortality above 98% after contact; however, the T4 concentration caused mortality of only 1.6%, while the Negative Control (NC) showed no mortality throughout the bioassay. The ants showed preference for uncontaminated environments, choosing it as the first area for displacement, with greater investment of time and frequency for displacement and self-cleaning activities (423 ± 0.16 s). However, they did not show interest in the attractive bait, probably due to the state of alert due to the contaminated area. Therefore, our results demonstrate that exposure to the insecticide Malathion causes a high mortality rate in O. brunneus, evidencing the potential risk of using the insecticide in urban areas, even though the species shows a preference for uncontaminated environments.