Effect of zinc toxicity on liver histology of Nile tilapia, Oreochromis niloticus
Abdel-Warith, Abdel-Wahab A. . 2011
In the present study the toxic effects of zinc (Zn) on the liver structure of Nile tilapia, Oreochromis
niloticus were investigated. Additionally, we estimated whether Zn concentration and exposure period
influence the degree and nature of histological changes in the liver of exposed fish. Two hundred and
forty fish (the average weight was 24.30± 2.85 g) were distributed randomly in twenty four glass aquaria
(80 L) with stocking density of 10 fish for each. The aquaria were divided into two groups: the first
group was exposed to 2, 4 and 6 mg/L of ZnCl2 which represent 0.25, 0.50 and 0.75 of Zn LC50
respectively for one week (short exposure period); while the second group was exposed to the same
concentrations of ZnCl2 with the same replicates for 4 weeks (long exposure period). In addition, control
group were not exposed fish to ZnCl2 (0.00 LC50) were stocked with three replicates for each period.
Fish mortality was significantly increased in a dose-dependent manner, without any significant effect of
the exposure duration. Histological changes in the liver included hepatocyte degeneration, nuclear
pycnosis, cellular swelling, and congestion of blood vessels. There was a marked difference in these
changes among the different treatments of Zn concentrations in addition to the intensity of histological
changes were however influenced by the extent of exposure period
Nile tilapia (Oreochromis niloticus) weighing 51.66 ± 2.42 g were exposed to 0%, 20%, 40%, and 60% of LC50 to either lead nitrate (Pb(NO3 )2 ) or copper sulfate (CuSO4 ) for 30 days.
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