SHORT-TERM TOXICITY ASSAY BASED ON DAPHNID FEEDING-BEHAVIOR

A rapid acute toxicity assay based on feeding behavior of Ceriodaphnia dubia was developed and evaluated. Feeding behavior was observed by staining yeast cells with a nontoxic stain (DTAF), which fluoresces under epifluorescent illumination, feeding the stained yeast to daphnids after they were exposed to toxicants for 6 hours, and observing the uptake of yeast by the daphnids. The endpoint of the test is the presence or absence of fluorescence in the daphnid gut. An exposure time of 6 hours was utilized so that the test could be completed in one working day. The 6-hour feeding activity suppression assay was compared with the standard 48-hour acute bioassay for determining the toxicity of selected heavy metals, organic compounds, and industrial effluent samples. The EC(50)s of pure compounds obtained via the 6-hour and 48-hour tests were well correlated (P < 0.05). EC(50)s of industrial wastewaters obtained via the two tests were also correlated at the same level of significance. The 6-hour feeding activity suppression assay was generally more sensitive than the 48-hour acute bioassay.