Neurotoxic responses in brain of catla catla exposed to cypermethrin: A semiquantitative multibiomarker evaluation

Fish being in direct and continuous contact with water serve as ecologically relevant indicator of health of aquatic environment. Cypermethrin (CYP)(2), a pyrethroid pesticide is a potent neurotoxicant which induces adverse effects on non - target organisms, particularly fish. Present study was designed to evaluate in vivo effects of CYP on acetyl cholinesterase (AChE) activity, histopathology and ultra structure in brain of Catla catla. Fish was exposed to two sub-lethal concentrations of the pesticide (0.124 mu g/L and 0.41 mu g/L) for 45 days. Analysis of the brain tissue was done at an interval of 15, 30 and 45 days. Significant concentration and time dependent inhibition of AChE activity, and degree of tissue change (DTC3) with respect to control was observed in brain after the toxicant treatment. Light microscopy revealed several histoarchitectural lesions such as necrosis, oedema, vacuolization, spongiosis and gliosis. Transmission electron microscographs of the control fish depicted neurons surrounded by supporting neuroglial tissue. Mild to moderate cellular changes such as shrinkage of axoplasm, irregular nucleus and fragmented rough endoplasmic reticulum was observed after 15 days of exposure to the pesticide. Most severe cytological alterations noticed after prolonged exposure to the toxicant at higher concentration were degeneration and decompaction of myelin sheath, swollen, vacuolated mitochondria with fragmented cristae, and neuroglia featuring degenerated cells. Necrotic changes such as neuronal shrinkage, disintegration of plasma membrane and condensed chromatin, suggested apoptosis induction. The prevalence of partial or complete cristolysis in mitochondria indicates that oxidative phosphorylation was severely compromised. The observed biochemical & cellular changes reflect the neurotoxic potential of cypermethrin at environmentally relevant sub-lethal concentration to Catla catla.