Toxicigological and physiological effects of ammonia On Tilapia Oreochromis niloticus At different pH levels

Résumé

The toxicity (LC50 values) of ammonium chloride and unionized ammonia was tested on different sizes (10,15g) of Tilapia Oreochromis niloticus in wich different pH levels were controlled within the range of 6.5 – 8.5 obtained results showed that, within the same pH, the toxic effect of ammonia in terms of NH3 in creased at lower pH values. It is concluded that NH4 + exerts some measure of toxicity and / or that increased H+ concentration increases the toxicity of NH3. Tilapia Oreochromis niloticus (5g) were exposed to the 96- h LC50 of unionized ammonia (0.85mg NH3/1) at pH 7.5 (common pH level of the Libyan water ways). The changes of hemoglobin (Hb), heamtocrite (Ht) haematocrit (Ht), Sodium (Na+), Potassium (K+), Glucose, asperateamnotransferase (AST,E.2.6.1.1), alamnine aminotransferase (ALT,E.C.2.1.2), were recorded The obtained results showed that blood Hb significantly decreased only after 6and 96h of exposure while Ht significantly decreased directly after 6h of exposure. Serum Na+ and K+ showed general trend of increase during the entire experimental period (96h). glucose concentration showed initial significant increase then returned to less than the control value after 96h of exposure. The was only a significant decrease in AST, ALT after which the enzymes activity significantly increased till the end of the experimental period. The significance of these changes are discussed.