| Summary: | In recent decades, research and awareness of issues related to environmental exposure to xenobiotics has increased. Upon their arrival in the aquatic environment, xenobiotics can affect non-target organisms, endangering the balance of ecosystems. Thus, ecotoxicological tests have been used as early diagnostic tools (e.g. biomarkers). Inhibition of acetylcholinesterase (AChE) activity in fish has been widely used in ecotoxicological studies as an indicator of exposure to neurotoxic pollutants. However, establishing a link between different levels of biological organization is an important issue when assessing the impact of pollutants. Thus, assessment of behavioral responses should be incorporated in environmental studies, because behavior demonstrates the ability of an individual to interact directly with the surrounding environment. Based on these theoretical assumptions, this thesis sought to generate toxicological data for some anticholinesterasic compounds in a non-target species – for future risk assessments and / or environmental monitoring – for three classes of compounds, detergents (SDS), pesticides (chlorfenvinphos) and drugs (neostigmine and pyridostigmine). In this context, the fish Lepomis gibbosus (pumpkinseed) was selected as test-organism. It presents itself as a potential candidate as a test-organism in ecotoxicological tests because it is abundant, it has simple laboratory requirements, and it is not a threatened species. Initially, we performed a characterization of cholinesterases in the head and dorsal muscle of L. gibbosus. Then, we evaluated the effects of in vitro and in vivo exposures to the anionic detergent SDS and the organophosphate pesticide chlorfenvinphos on the AChE of L. gibbosus. In vivo exposures were also performed in order to evaluate the effects of the pharmaceutical drugs neostigmine and pyridostigmine on the activity of AChE (head and dorsal muscle). During these experiences, a behavioral trial was assayed for assessing possible changes in L. gibbosus after exposure to these xenobiotics. Results showed that acetylcholinesterase is the predominant enzymatic form in the head and muscle of L. gibbosus. Exposure to chlorfenvinphos showed inhibition of AChE activity both in vivo and in vitro, unlike SDS - which showed no inhibitory effects. For pharmaceutical drugs, inhibitory effects on AChE were recorded, particularly in the case of pyridostigmine, in the head of L. gibbosus. However, there were no concomitant significant changes in behavioral parameters of exposed animals, compared to untreated organisms.
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