Abstract
Acute toxicity tests (96-hr LC50 and lethal concentration) of chromium (Cr) and cadmium (Cd) were conducted with two fish
species viz. Channa marulius and Wallago attu. At the end of each trial, the fish were dissected and their organs viz. gills,
kidney and liver were isolated for the determination of antioxidant enzymes activity. Cadmium was significantly more toxic
than chromium with the mean 96-hr LC50 values of 75.70 ± 0.91 and 94.86 ± 0.96 mg L-1, respectively. C. marulius was
significantly less sensitive than W. attu. Activity of superoxide dismutase increased with increasing metallic ion
concentrations in the test mediums for both fish species. However, the activity of catalase and peroxidase decreased by
increasing the concentration of metallic ions in the test mediums. The fish kept in control conditions (without metal stress)
showed maximum activity of catalase and peroxidase. The fish, C. marulius accumulates significantly higher contents of
chromium than cadmium. Among fish organs, liver appeared as a target organ that accumulate significantly higher contents
of chromium followed by that of kidney, gills, fins, skin, muscle and bones. The W. attu followed almost the similar trend as
that of C. marulius for the accumulation of metals. The accumulation order of metals in fish organs were
liver>kidney>gills>fins>skin>muscle>bones for both fish species
