Histopathological responses in liver, brain and gills of Oreochromis niloticus juveniles exposed to water soluble fractions of crude oil

Abstract

Aquatic pollution has been shown to induce different changes ranging from biochemical alterations in single cells to changes in whole  populations. In this study, qualitative analyses of liver, brain and gills histopathological parameters were evaluated in Oreochromis  niloticus after exposure to water-soluble fractions of crude oil. After preliminary short-term (96 hours) bioassay, fish were subjected to  four sublethal concentrations (30, 45, 60, and 75 % of the LC₅₀ corresponding to 28, 41, 55, and 69 mg/l respectively), and a control group  using a semi-static renewal method for 90 days. After the exposure period, the liver, brain and gills were harvested, labeled and prepared  for photomicrography using standard procedure. Results showed atrophy and necrosis of hepatocytes and degeneration of hepatopancreas in the liver. The histopathological alterations in the brain included mild congestion of cerebral blood vessels, widespread  vacuolation of neuropil, necrosis and atrophy of neurons. In the gills, congestion of capillaries, atrophied and necrotic lamellae were  detected. Overall, the study revealed that histopathological biomarkers can be relied upon as a suitable tool for accessing long-term  impacts of crude oil spillage in the aquatic environment. Therefore, an immediate multi-agency response approach for efficient and  effective management of oil spills is recommended.