[
2000]
Computer tracking of Caenorhabditis elegans, a free-living soil nematode, is a promising tool to assess behavioral changes upon exposure to contaminants. A short life cycle, a known genetic make-up, thoroughly studied behavior, and a completely mapped nervous system make C. elegans an attractive soil test organism with many advantages over the commonly used earthworm. Although many toxicity tests have been performed with C. elegans, the majority focused on mortality, a much less sensitive endpoint than behavior. A computer tracking system has been developed to monitor behavioral changes using C. elegans. Because conditions unrelated to specific toxicant exposures, such as changes in temperature, developmental stage, and presence of adequate food sources, can affect behavior, there is a need to standardize tracking procedures. To this end, we have developed reference charts for control movement comparing the movement of four and five day-old adult nematodes. The use of K-medium versus deionized (DI) H2O for pre-tracking rinses was also investigated. A final reference chart compared the behavioral responses of nematodes at various food densities (i.e. bacterial concentrations).
[
2000]
There is growing interest in the use of bioindicators to assess metal toxicity in soil. The current ASTM Standard Guide for Conducting Laboratory Soil Toxicity Test with the lumbricid earthworm Eisenia fetida (E 1676-97) uses a common earthworm. The nematode Caenorhabditis elegans is a natural soil inhabitant with many characteristics that make an ideal alternate test organism. It has been used to assess metal toxicity in aquatic media, agar plates and in soil. Work is currently underway on the design of a C. elegans procedure for metals in soil. The objective of this study was to determine differences in LC50S between the chloride salt and the nitrate salt forms of cadmium, copper, lead, nickel, and zinc, in three types of soil: Cecil, Tifton, and ASTM artificial soil. Results indicated that the toxicological effect of the metallic salt varies and is dependent on the particular metal. For Cd and Pb the nitrate form is more toxic while Cu and Ni are more toxic in the chloride form. The composition of the soil also effected toxicity, with the metal being the least toxic in ASTM soil and more toxic in the Tifton soil. This strongly correlated with organic matter and clay content of the soil. It is important to determine the effects of carrier salt form and soil composition on metal toxicity, not only in order to standardize the protocol for C. elegans soil toxicity testing, but also in establishing acceptable exposure concentrations in the soil.