The effects of environmental nickel toxicity upon survival, growth, reproduction, fecundity, and lifespan of nematodes Caenorhabditis elegans, Pristionchus pacificus, and Caenorhabditis briggsae

Nickel (II) is a common component of many natural products and man-made devices. Due to its frequent use in everyday life, relatively large amounts of nickel are being released into the environment. Nickel, however, is a known carcinogen; therefore, an assay must be developed in order to understand the toxic effects of this heavy metal on living organisms. Nematodes are a model animal species that have been used in sediment and water testing of contaminated environmental samples. Nematodes lend themselves perfectly to liquid and sediment assays due to their easy recovery, handling, distinction between larva and adults, and short life cycle. In this study, we used three nematode species, Caenorhabditis elegans, Pristionchus pacificus, and Caenorhabditis briggsae, in order to determine the effects of nickel on the survival, growth, reproduction, fecundity, and lifespan of these model biotic organisms. During preliminary testing, C. briggsae displayed highly variable results during both sediment and liquid assays. Thus, the majority of testing in this project was performed on C. elegans and P. pacificus. We found that C. elegans is best suited for environmental assays where there is a large portion of dissolved organic carbon in the sediment. However, P. pacificus, displayed no preference for any of the soil physio-chemical characteristics during these assays. The element Nickel (II) can either bind to substrates within a sediment, or can freely move through aqueous solution. In this study, we showed that nickel bound in sediment is highly lethal to the P0 generation of nematodes; however, the effects of nickel bound in sediment were not readily apparent on the F1 generation of both C. elegans and P. pacificus. Using liquid assays, we also determined that aqueous nickel was not detrimental to the P0 generation for all three nematode species. Interestingly, higher dosages of aqueous nickel were shown to be detrimental to the F1 generation for C. elegans, whereas P. pacificus showed no decline in the number of F1 progeny recovered. Finally, our results show that nickel bound in sediment also has an effect on longevity. Using C. elegans strain JK574: Cel-fog-2 (q71) LGV in a longevity trial, it was determined that higher dosages of bound nickel can decrease the number of days needed to reach a 50% recovery rate by 7-8 times. Overall, the results of these experiments show that both C. elegans and P. pacificus can be used as bio-indicators of nickel contaminated water and sediment samples. By developing this quick, efficient, and reliable assay, other laboratories will be able to determine the amount of nickel that can be detrimental in various ecological samples and what the toxic effects of this metal will be on living organisms.M.S