Abstract
Biomarkers are frequently used in ecotoxicology as they allow to study toxicant effects happening at low concentrations of exposure. However, most sublethal studies only evaluate cellular biomarkers which lack evident ecological relevance. We used a multibiomarker approach to estimate the toxic effects of ethoprophos, an organophosphate insecticide commonly used in banana plantations, on the tropical fish Astyanax aeneus (Characidae). We measured biomarkers at sub-individual (cellular) and individual (metabolism, behavior) levels and examined relationships among these responses. A sublethal exposure to ethoprophos caused a significant (54%) reduction of brain Cholinesterase (ChE) activity, reflecting the pesticide’s high neurotoxicity. However, other biomarkers like oxidative stress, biotransformation reactions, and resting metabolic rate were not affected. Exposure to ethoprophos modified antipredator behaviors such as escape response and detection avoidance (light/dark preference): exposed fish escaped slower from a simulated attack and preferred brighter areas in a novel tank. The relationship between ChE activity and reaction time suggests that pesticide-induced ChE inhibition reduces escape ability in fish. Our results provide evidence that impacts of organophosphate pesticides on fish ecological fitness can occur even with short exposures at very low concentrations.
Highlights
Tropical freshwater and estuarine systems are highly impacted by the continuous discharge of pesticides from agricultural activities, especially in regions with poor regulation and control like Central America[1,2,3]
Considering the usefulness of linking biochemical, physiological and behavioural endpoints to better predict the effects of toxicants exposure on fish populations, we proposed to use a suite of biomarkers and individual responses to study the toxic effects of ethoprophos, an organophosphate pesticide commonly used in banana plantations, on Astyanax aeneus (Characidae), a native freshwater fish from Central America
Our results showed that exposure to a low sublethal concentration of the organophosphate pesticide ethoprophos has a neurotoxic effect on fish that correlates with a slow escape response to predator attack
Summary
Tropical freshwater and estuarine systems are highly impacted by the continuous discharge of pesticides from agricultural activities, especially in regions with poor regulation and control like Central America[1,2,3]. Sub-individual biomarkers comprise subtle cellular processes related to the metabolism of xenobiotics (e.g., transferases, and hydrolases), as well as molecular alterations related to the mode of action of the substance (e.g., ChE inhibition, oxidative stress)[16] These cellular biomarkers are often used to understand the mechanisms of toxicity, alone they are poor predictors of the ecological implications of pesticide exposure[17]. Whether exposure to environmentally relevant concentrations of OPs and the associated level of ChE inhibition, can still affect the individual performance of fish Aside from their neurotoxicity, organophosphates can increase cellular oxidative stress, by affecting antioxidant defense responses like catalase enzyme activity (CAT) and leading to cellular damage e.g. membrane lipid peroxidation (LPO)[22,23]. The inclusion of diverse biochemical biomarkers improves the assessment of the OPs effects at the sub-individual level and potential mechanisms of their toxicity
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