M. Alishahi
A. Mohammadi
M. Mesbah
M. Razi Jalali

The present research aimed to determine acute toxicity and evaluate the effect of sub-lethal concentrations of diazinon on some haematological and immunological parameters of Barbus sharpeyi by the Organization for Economic Cooperation and Development methods. Juvenile B. sharpeyi were exposed to ۰, ۵%, ۱۰% and ۲۵% ۹۶h LC۵۰ concentrations of diazinon for ۲۱ days. Blood samples were taken after ۷, ۱۴ and ۲۱ days of exposure to diazinon. Haematological and biochemical parameters including: RBC, Hb, PCV and WBC, as well as serum enzymes were evaluated. Immunological indices and resistance against bacterial infection, were determined. Results showed that ۹۶h LC۵۰ of diazinon in B. sharpeyi was estimated at ۳.۹۸۷ mg/L. Diazinon toxicity at a level of ۱ and ۰.۴ mg/L decreased RBC, Hb, and Hematocrite, in almost all sampling periods compared. WBC and globular index decreased significantly in fish exposed to ۱ mg/L diazinon on days ۱۴ and ۲۱(p<۰.۰۵). Dose dependent increase in serum enzymes were seen in fish exposed to diazinon. Diazinon toxicity showed no effect on serum LDH level (p>۰.۰۵). Dose dependent decrease in serum total protein and globulin were indicated in diazinon exposed fish. Serum lysozyme and bactericidal activity decreased in T۳ and T۴ at days ۱۴ and ۲۱. Mortality following challenge to A.hydrophila increased in fish exposed to ۱ mg/l diazinon. It can be concluded that diazinon is toxic to B. sharpeyi. Therefore, the strict biosecurity should be taken into consideration when this pesticide is used in agricultural fields surrounding freshwater sources of fish cultivation

Diazinon, Toxicity, Barbus sharpeyi, Immunological parameters, Hematology