Differential Toxicities of Nickel Salts to the Nematode Caenorhabditis elegans

This study focused on assessing whether nickel (Ni) toxicity to the nematode Caenorhabditis elegans was affected by the molecular structure of the Ni salt used. Nematodes were exposed to seven Ni salts [Ni sulfate hexahydrate (NiSO4 center dot 6H(2)O), Ni chloride hexahydrate (NiCl2 center dot 6H(2)O), Ni acetate tetrahydrate (Ni(OCOCH3)(2)center dot 4H(2)O), Ni nitrate hexahydrate (N2NiO6 center dot 6H(2)O), anhydrous Ni iodide (NiI2), Ni sulfamate hydrate (Ni(SO3NH2)(2)center dot H2O), and Ni fluoride tetrahydrate (NiF2 center dot 4H(2)O)] in an aquatic medium for 24 h, and lethality curves were generated and analyzed. Ni fluoride, Ni iodide, and Ni chloride were most toxic to C. elegans, followed by Ni nitrate, Ni sulfamate, Ni acetate, and Ni sulfate. The LC50 values of the halogen-containing salts were statistically different from the corresponding value of the least toxic salt, Ni sulfate. This finding is consistent with the expected high bioavailability of free Ni ions in halide solutions. We recommend that the halide salts be used in future Ni testing involving aquatic invertebrates.