Application of blood biomarker for determination of Diazinon and Malathion toxicity to Big-head Carp (Hypophthalmichthys nobilis)

Malathion and diazinon are widely used organophosphate pesticides in the agriculture fields, especially in the north provinces of Iran. In the current study, lethal concentrations of diazinon and malathion were determined based on big head carp calculated death rates at 24, 48, 72 and 96 hours using probit analysis. Then, in a separate experiment and according to the obtained LC50, the effects of these toxins on fish hematological parameters was evaluated in which fish were disturbed in 10 treatments with 3 replicates (4 different doses of diazinon, 4 different doses of malathion and 1 control for each toxin) for 7 days. Fish were exposed to different sub-lethal concentrations of each toxin (12.5, 25, 37.5 and 75% of lethal concentration (LC50 96h). After 7 days, blood samples were collected and hematological parameters including hematocrit, hemoglobin, red blood cells count, the total number of white blood cells and white blood cell differential count (the percentage of lymphocytes, monocytes, neutrophils and eosinophils) were examined. The results of acute toxicity test showed that diazinon is more toxic to big head carp compared to malathion. Also, hematological studies of big head carp exposed to diazinon showed a significant reduction in red blood cells and white blood cells with increasing toxin concentration. Meanwhile, the percentage of neutrophils remarkably increased while lymphocytes significantly decreased along with increasing the concentration of diazinon.