Abstract

Potassium permanganate (KMnO₄) is an oxidizing agent used in aquaculture for many years. Despite its known efficacy for the treatment and prevention of fish diseases, information about their potential toxicity in non-target organisms is still very limited. The objective of this study was to evaluate the sublethal effects of potassium permanganate (1.0 and 4.0 mg L^-1) on Nile tilapia, Oreochromis niloticus, using hematological analysis and oxidative stress (reduced glutathione concentration, glutathione S-transferase activity, catalase and lipid peroxidation) as biomarkers. Fish exposed to a concentration at 1.0 mg L^-1 had no significant variations in blood parameters. At 4.0 mg L^-1, the changes in hematological parameters of the exposed animals indicated hemolysis as a result of the oxidizing action of potassium permanganate. Regarding the oxidative stress analyses, only the reduced glutathione presented significant increase in fish exposed to potassium permanganate, indicating adaptive and protection responses against the oxidative stress. This study demonstrated that concentrations of potassium permanganate (1.0 to 4.0 mg L⁻¹) usually recommended for the treatment of fish diseases, can be toxic to Nile tilapia (O. niloticus).

Key words: Potassium permanganate, Nile tilapia, hematology, oxidative stress.