Toxicity of Metals to a Freshwater Snail,Melanoides tuberculata
Adult freshwater snailsMelanoides tuberculata(Gastropod, Thiaridae) were exposed for a four-day period in laboratory conditions to a range of copper (Cu), cadmium (Cd), zinc (Zn), lead (Pb), nickel (Ni), iron (Fe), aluminium (Al), and manganese (Mn) concentrations. Mortality was assessed and median lethal times (LT50) and concentrations (LC50) were calculated. LT50and LC50increased with the decrease in mean exposure concentrations and times, respectively, for all metals. The LC50values for the 96-hour exposures to Cu, Cd, Zn, Pb, Ni, Fe, Al, and Mn were 0.14, 1.49, 3.90, 6.82, 8.46, 8.49, 68.23, and 45.59 mg L−1, respectively. Cu was the most toxic metal toM. tuberculata, followed by Cd, Zn, Pb, Ni, Fe, Mn, and Al (Cu > Cd > Zn > Pb > Ni > Fe > Mn > Al). Metals bioconcentration inM. tuberculataincreases with exposure to increasing concentrations and Cu has the highest accumulation (concentration factor) in the soft tissues. A comparison of LC50values for metals for this species with those for other freshwater gastropods reveals thatM. tuberculatais equally sensitive to metals.