Acute Toxicity of Some Heavy Metals on Zebrafish, Danio rerio

Water pollution by industrial effluent containing heavy metals pose a serious hazard to the aquatic biota as well as human. They are non bio-degradable and can accumulate in the environment and enter the food cycle. When the amount of heavy metals inthe medium reach to more than a certain limit it become toxic for those animals that live in that environment. The heavy metals chiefly include lead (Pb), mercury (Hg), cadmium (Cd), silver (Ag), zinc (Zn), nickel (Ni), manganese (Mg) and chromium (Cr). The present study deals with the acute toxicity of Zn, Ni and Cr on zebrafish, Danio rerio. The semi-static test method was used. The 96-h LC₅₀ of Zn was 80.96 mg/L, for Ni it was 124.78 mg/Land 45.59 mg/L forCr. The toxicity ranking of these metals is Cr>Zn>Ni. Thus, it is concluded from the present study that zebrafish are highly sensitive to Zn, Ni and Cr and can be used as a bio-indicator organism of aquatic pollution. Further work with toxicity testing methods directly on fish will be useful in assessing possible ecological risk of heavy metals.