Short‐term toxicity assay based on daphnid feeding behavior

A rapid acute toxicity assay based on feeding behavior of Ceriodaphina 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 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.