Cholinesterase inhibition and behavioral toxicity of carbofuran on Oreochromis niloticus early life stages

• Published in: Aquatic toxicology 2011-10, Vol.105 (3), p.312-320
• Main Authors: Pessoa, P.C., Luchmann, K.H., Ribeiro, A.B., Veras, M.M., Correa, J.R.M.B., Nogueira, A.J., Bainy, A.C.D., Carvalho, P.S.M.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Applied ecology; Behavior, Animal - drug effects; Biological and medical sciences; biomarkers; Brackish; Carbofuran; Carbofuran - toxicity; Cholinesterase; Cholinesterase Inhibitors - toxicity; Cichlids - physiology; Daphnia; Daphnia magna; Dose-Response Relationship, Drug; Ecotoxicology, biological effects of pollution; enzyme activity; fish; Fresh water ecosystems; Fundamental and applied biological sciences. Psychology; General aspects; Growth; insecticides; Insecticides - toxicity; Larva - physiology; lethal concentration 50; Lethal Dose 50; Models, Biological; mortality; nauplii; No-Observed-Adverse-Effect Level; Oreochromis niloticus; Oreochromis niloticus larvae; Predator–prey; recruitment; Swimming; Synecology; toxicity; Vision; Water Pollutants, Chemical - toxicity
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2011.06.020

► Sublethal exposure of tilapia to carbofuran causes cholinesterase activity inhibition. ► Visual and growth deficits were more sensitive than cholinesterase inhibition. ► Cholinesterase inhibition correlates with behavioral effects that fit ecology models. Nile tilapia Oreochromis niloticus at 9 days post-hatch were exposed in semi-static experiments to the carbamate insecticide carbofuran, which is applied in agricultural systems in Brazil. Although the molecular mechanism of carbofuran toxicity is well known, a detailed understanding of the ecological mechanisms through which carbofuran effects can propagate towards higher levels of biological organization in fish is incomplete. Mortality rates were quantified for larvae exposed for 96 h to 8.3, 40.6, 69.9, 140, 297 and 397 μg/L carbofuran, and the LC 50 96 h was 214.7 μg/L. In addition, the biochemical biomarker cholinesterase inhibition and behavioral biomarkers related to vision, swimming, prey capture and predator avoidance were quantified in individual larvae, as well as their growth in weight. The behavioral parameters were quantified by analysis of digitally recorded videos of individual larvae within appropriate experimental setups. The activity of the enzyme cholinesterase decreased after exposure to carbofuran with a lowest observed effects concentration (LOEC) of 69.9 μg/L. Visual acuity deficits were detected after carbofuran exposure with a LOEC of 40.6 μg/L. Swimming speed decreased with carbofuran exposure, with a LOEC of 397.6 μg/L. The number of attacks to prey ( Daphnia magna nauplii) decreased in larvae exposed to carbofuran, with a LOEC of 397.6 μg/L. Growth in weight was significantly reduced in a dose dependent manner, and all carbofuran groups exhibited a statistically significant decrease in growth when compared to controls ( p < 0.05). The number of predator attacks necessary to capture larvae decreased after exposure to carbofuran, and the LOEC was 69.9 μg/L. These results show that exposure of sensitive early life stages of tilapia O. niloticus to sublethal concentrations of carbofuran can affect fundamental aspects of fish larval ecology that are relevant to recruitment of fish populations, and that can be better understood by the application of behavioral biomarkers.