Biochemical and Histopathological Changes Induced by Nickel in the Striped Mullet, Mugil cephalus (Linnaeus 1758)

The present study is focused on determining the acute and chronic toxicity of nickel (Ni) to fish fingerlings, Mugil cephalus. The 96-h median lethal concentration (LC₅₀) for Ni was found to be 42.2 ± 3.9 mg L^-1. Based on the chronic toxicity test for 30 days, "No Observed Effect Concentration", "Lowest Observed Effect Concentration" and "Chronic value" were found to be 2.9 ± 0.14, 4.7 ± 0.14 and 3.7 ± 0.14 mg Ni L^-1, respectively. The activities of biomarker enzymes including esterase, superoxide dismutase and malate dehydrogenase showed differential expression and cellular anomalies like hyperplasia and detachment of bipolar cells from photoreceptor cells in the retina of eye of mullet. Cellular anomalies in the retina of fish eye affect the primary function of retina, which is to convert light energy into nerve impulses transferred to the brain via the optic nerve, leading to loss or poor vision.