Sediment Filter (TK Multitrade, Seri Kembangan, Malaysia)) aerated through an air stone. During 3-deazaneplanocin acclimation the snails were fed on lettuce. The standard stock solution (100mgL?1) of Cu, Cd, Zn, Pb, Ni, Fe, Al, and Mn was prepared from analytical grade metallic salts of CuSO4?5H2O, CdCl2?2.5H2O, ZnSO4?7H2O, Pb(NO3)2, NiSO4?6H20, FeCl3, Al2(SO4)3?18H2O, and MnSO4?H2O, respectively (Merck, Darmstadt, Germany). The stock solutions were prepared with deionized water in 1L volumetric flasks. Acute Cu, Cd, Zn, Pb, Ni, Fe, Al, and Mn toxicity experiments were performed for a four-day period using adult snails (shell length approximately 1.5�C2.0cm, mean wet weight 22.5 �� 1.6mg) obtained from stocking tanks. Following a range finding test, five Cu, Cd, Zn, Pb, Ni, Fe, Al, and Mn nominal concentrations were chosen (Table 1).

Metal solutions were prepared by dilution of a stock solution with dechlorinated tap water. A control with dechlorinated tap water only was also used. The tests were carried out under static conditions with renewal of the solution every two days. Control and metal-treated groups each consisted of two replicates of five randomly allocated snails in a 500mL glass beaker containing 400mL of the appropriate solution. No stress was observed for the snails in the solution, indicated by 100% survival for the snails in the control water until the end of the study. A total of 10 animals per treatment/concentration were used in the experiment and a total of 410 animals were employed in the investigation [42, 43].

Samples of water for metal analysis taken before and immediately after each solution renewal were acidified to 1% with ARISTAR nitric acid (65%) (BDH Inc, VWR International Ltd., England) before metal analysis by flame or furnace Atomic Absorption Spectrophotometer (AAS-Perkin Elmer model AAnalyst800, Massachusetts, USA) depending on the concentrations.Table 1Median lethal times (LT50) for M. tuberculata exposed to different concentrations for Cu, Cd, Zn, Pb, Ni, Fe, Al, and Mn.During the toxicity test, the snails were not fed. The experiments were performed at room temperature of 28�C30��C with photoperiod 12h light:12h darkness, using fluorescent lights (334�C376 lux). Water quality parameters (pH, conductivity, and dissolved oxygen) were measured every two days using portable meters (model Hydrolab Quanta, Hach, Loveland, USA) and water hardness samples were fixed with ARISTAR nitric acid and measured by flame atomic absorption spectrophotometer (AAS��Perkin Elmer model AAnalyst 800). Mortality was recorded every 3 to 4 hours for the first two days and then at 12 to 24 hour intervals throughout the rest of the test period. The criterion used to determine mortality Batimastat were failure to respond to gentle physical stimulation.