Lethal and sub-Lethal Toxicity of Chlorphyrifos on Fish Rohu( Labeo Rohita Hamilton, 1822)
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Department of Zoology
Abstract
Chlorpyrifos is an organophosphate insecticide which is commercially used to control
insect pest. It is second largest selling organophosphate and found to be more toxic to fish.
Present study was performed to determine the acute toxicity of Chlorpyrifos (LC50
), their
behavioural changes after exposure to pesticide and also haematological study of Rohu
(Labeo rohita). Acute toxicity test was accompanied following the standard method
(OECD 203 testing guidelines, 1992). In treated fish alterations in various behavioural
patterns respiratory metabolism, opercular beat rate and blood parameters were examined
for sub-lethal end-points following 1 h, 24 h, 48 h, 72 h, and 96 h exposure. The LC50
value
of Chlorpyrifos was found to be 0.362 mg/L. Behavioural changes were also observed in
control and exposed fish. Schooling behaviour was observed to be disrupted in first day
after exposure to pesticide. High opercular beat rate (p < 0.01) at 24 h and (p < 0.001) from
48-96 h and oxygen consumption rate was recorded in pesticide-exposed groups in
comparison to control. The pesticide stress caused a significant elevation in haemoglobin
(p <0.01). Glucose and protein content was found to be increased (p > 0.05) in the pesticide
group, compared to the control. Some general behavioural changes such as erratic
movement, gulping, schooling, mucus secretion, equilibrium, aggregating behaviour, and
paleness in the body were observed in pesticide-exposed fish. The current study revealed
that CPF was found to be highly toxic pesticide. Hence, its discriminate use should be
avoided as it can contribute to decline of Rohu in natural habitat.