Toxic manifestations of mercuric chloride and polychlorinated biphenyls on the haematological aspects of Danio rerio

Objectives: To explore the acute toxicity of major aquatic pollutants like mercuric chloride (HgCl2) and polychlorinated by phenyls (PCB) and their effects based on the haematology of fresh water fish Danio rerio (Zebra fish).Methods: Zebra fish (Danio rerio) were exposed to progressive concentrations of HgCl2 and PCB. The fishes were exposed to various concentrations of 5, 10, 20, 30, 40, 50 and 60 µg/L of mercury and PCB for a period up to two weeks. Haematological tests (total RBC, WBC count and haemoglobin concentration) were carried out on each concentration as well as control for a period of 2 weeks.Results: It was observed that, in exposure time from 0, 7 and 14 days, the total erythrocyte (RBC), leucocytes (WBC) haemoglobin (Hb) values decreased. The exposure to sub lethal doses of Mercury and PCB for 1, 7 and 14 days exposure period causes significant(Values are  expressed as means ± SD. Significant difference between groups were  compared to control, *p <0.01, **p <0.05) time and dose dependent alterations in total RBC, WBC and haemoglobin count compared to the control values.Conclusions: Haematological parameters constitute one of the important methods to access the health or ill health of an organism, subjected to intoxication. This demonstrates the physiological dysfunction of the haemopoietic system. Hgcl2 is a heavy metal that causes symptoms in human like and gastrointestinal disturbances, anaemia, anorexia, loss of weight, chronic inflammations of kidneys. PCB exposure in animals has been reported to develop Wasting syndrome, reduced body weight, immune toxicity, vitamin A deficiency, and thyroid hormone deficiency, reproductive effects in offspring like reduced birth weight, abnormal gonad development. It also affect the central nervous system which results in slowed learning and memory loss, and also responsible for other behavioural changes. Thus toxicity bioassay is the basic tool for the detection, evaluation and abatement of water pollution