Histopathological responses and recovery in gills and liver of Nile tilapia (Oreochromis niloticus) exposed to diesel oil

Abstract

Water pollution due to crude oil has become one of the major means of pollution lately. We experimented to study to what extent different concentrations of diesel oil can distress the gills and liver of the affected fish. Two groups of Nile tilapia (Oreochromis niloticus) were exposed to 0.1 ml/l and 0.5 ml/l diesel oil for seven days and then kept in pollutant-free water for 14 days to scrutinize how much they can recover. A control group has also maintained during the experiment. Several histo-pathological abnormalities were observed in gills including deformed pillar system, clubbed tips in the secondary lamellae, hyperplasia of the epithelial cells, aggregation of cells of the primary lamellae, fusion of secondary lamellae, telangiectasia and lamellar aneurysms. Though almost similar level of aberration was observed in the lower and higher treatment group, fish treated with lower concentrations were quick to recover. When it comes to the liver, fish treated with 0.1 ml/l diesel showed mild necrosis, patchy degeneration, hypertrophy nucleus and which eventually recovered after 14 days of the recovery period, whereas fish treated with 0.5 ml/l diesel showed moderate to severe abnormalities in almost all cases and the recovery was less but pattern was observed. The experimental study concluded that the higher the exposure to diesel oil, higher incidences of major health problems are recorded, seriously piercing the healing system of Nile tilapia.