Determination of Lethal Concentration (LC50 96 H) of Diazinon and Effects on Histological and Hematological Parameters on Sterlet (Acipenser Ruthenus)

A study was conducted to determine LC50 96h of Diazinon (an organophosphate insecticide) on juvenile Sterlet sturgeon (Acipenser ruthenus) at Shaheed Beheshti Sturgeon Hatchery (Rasht, Guilan, Iran). For this purpose, 180 juvenile Sterlet sturgeon (mean weight of 6.48±1.39 g) were used. Fish were randomly placed in 6 groups each with 3 replicates (five experimental treatments and a control group) in fiberglass tanks (75×50×15 cm). The experiments were carried out in static method according to Organization of Economic Cooperation and Development guidelines (O.E.C.D) for 96 hours. Physio-chemical parameters of water including temperature, oxygen, pH and total hardness were measured regularly throughout the study. Juvenile Sterlet specimens were subjected to concentrations of 3, 3.41, 3.87, 4.4 and 5 ppm and Probit analysis suggested the LC10, LC50, LC96 concentrations as 2.48, 3.56 and 5.17 ppm respectively. In hematological studies values of RBC, WBC and PCV were significantly varied in in experimental and control groups (P< 0.05). Exposure to Diazinon induced curvature of the spine, body trembling, rapid swimming and whirling, pale color, bruise on the head with eventual sinking to the bottom of the aquarium and death. Examination of gills showed edema and fusion in primary lamellae, swelling and fusion of secondary lamella, vacuole bearing, flattened and flaked secondary lamellae, separation of cells, necrosis and general hemorrhage with higher intensity at 4.4 and 5 mg/l concentrations. In liver tissues also edema, vacuole bearing cells, damage to cytoplasmic membrane, loss of granular appearance of the cytoplasm, pyknotic nuclei, karyolysis, karyorrhexis, necrosis and complete breakdown of the cell membrane at 4.4 and 5 mg per liter treatments were more likely than other treatments.