DOI: 10.36347/sajb.2015.v03i01.011

Pages: 52-56

Toxicity tests using early life stages of fish are of great importance in assessing risks to growth, reproduction and survival in polluted environments and are important tools for good environmental monitoring. The present study deals with the effect of heavy metals (zinc, nickel and chromium) on the embryo and larvae of zebrafish, Danio rerio. Embryo were exposed to Zn (10, 20, 30, 40, 50 mg/l), Ni (40, 50, 60, 70, 80 mg/l) and Cr (7, 12, 17, 22, 27 mg/l) however, larvae were exposed to 4, 9, 14, 19, 24 mg/l Zn, 15, 20, 25, 30, 35 mg/l Ni and 3, 6, 9, 12, 15 mg/l Cr. The 72-h LC50 value for embryo is 41.08 mg/l for Zn, 69.78 mg/l for Ni and 15.99 mg/l for Cr. The 24 to 96-h LC50 value for the larvae showed a gradual decrease as the exposure time was increased. The 96-h LC50 for larvae is 12.01 mg/l for Zn, 31.13 mg/l for Ni and 6.24 mg/l for Cr. The toxicity was concentration as well as time dependent. Toxicity tests revealed that larvae of zebrafish are more sensitive to heavy metals as compared to the embryos. The probable causes have been discussed.