Pesticides are a fatal threat to the non-target organisms in the aquatic system. The present study was aimed to explore the effect of chlorpyrifos (CPF), an organophosphate (OP) on a fresh water teleost, Heteropneustes fossilis. LC50 for 96h was found to be 1.921 mg/l. The fishes were sacrificed after 96h of exposure and tissues (gill, liver, and kidney) were collected and were further processed for histopathological studies. Collected blood was processed for haematological studies. Significant decrease (p < 0.05) in various haematological parameters i.e. total number of RBCs, % haemoglobin, hematocrit, MCV, MCH and MCHC was noted while a significant increase in WBCs particularly, neutrophils was recorded (p < 0.01) upon exposure. Histopathological studies of the treatment group showed significant destruction of histo-architechture of all of the tissues in comparison to control. This preliminary study reflects the impact of CPF on organ and blood physiology of Heteropneustes fossilis.
