Thesis defence by Nicresse Guedegba

Effets de l’exposition ex situ et in situ des juvéniles du tilapia du Nil Oreochromis niloticus à des pesticides utilisés dans le traitement phytosanitaire du cotonnier au Bénin via l’approche multi-biomarqueurs

Cotton crop is one of the most pesticide-intensive crops in the world. In Benin, cotton is the principal source of income. It is especially grown in the North, where also the majority of the country’s water reservoirs can be found. This study evaluates the effects of pesticides applied in cotton crops on the fish produced in the reservoirs with Nile tilapia (Oreochromis niloticus) as study species. First, acute toxicity was tested to determine the CL₅₀ – 96h of ACER-35EC, a commonly used pesticide. Second, a chronic toxicity test evaluated the effects of the pesticide’s components on several toxicity biomarkers (neurotoxicity, reprotoxicity, immunotoxicity, hepatotoxicity, oxidative stress, etc.). Finally, the effects of molecules found in low and highly contaminated water reservoirs were compared. Effects were observed in the nervous (ChE), immune (activity of complement, lysozyme, production of superoxide anions), and endocrine system (sex steroids, Vtg) as well as in the histology of gonad, liver and kidney tissues. With these results, an Integrated Biomarker Response (IBR) index is calculated to easily assess the impact of the pesticides at different concentrations, for different exposure times and depending on the sex of the fish.

More information in French.

Nicresse will present the results of her PhD thesis, conducted in the Research Unit of Environmental and Evolutionary Biology (URBE) under the supervision of Patrick Kestemont. (The presentation will be in French)