Résumé
The study was undertaken to establish a sub-lethal concentrations (0.0002, 0.002, 0.02mg/L) toxicity of mercuric chloride in Egyptian catfish (Clarias lazera) after long-term (14 days) exposure which achieved by investigation of some selective hematological and biochemical parameters with respect to erythrocyte morphological alterations. Experimental fish were set up with three groups for each concentration, plus the control group. Blood samples were collected from five individuals for each concentration after 14 days of exposure. The hematological parameters analyzed were: total red blood cell count (RBC), hemoglobin concentration (Hb), packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), total platelets count, total white blood cell count (WBC) and differential leukocyte counts (neutrophil, eosinophil, lymphocyte, monocyte and basophils). Fish exposed to 0.02mg/L Hg for a long time showed a significant decrease in RBC count, Hb, MCHC and platelets number than control groups (P<0.05) with moderate elevations in PCV, MCV, WBC, neutrophil, eosinophil, lymphocyte count, glucose and cortisol level compared to the control groups (P<0.05). However, fish exposed to the other two low concentrations showed no toxic effects. Hg at the concentrations studied was toxic to Egyptian catfish (Clarias lazera) at the higher dose only (0.02mg/L) after long term exposure.