A four‐day survival and reproduction toxicity test for ceriodaphnia dubia

A 4-d survival and reproduction toxicity test utilizing Ceriodaphnia dubia has been developed and evaluated. This toxicity test has been compared to the standard 7-d test using a total of 12 toxicants encompassing a wide range of chemical classes. In addition, 48-h LC50 values were determined for each chemical in the absence of food. Four-day and seven-day tests were run concurrently, twice for each chemical. Less-than-12-h-old neonates for both 4-d and 7-d tests were segregated into individual test cups on Fridays. Animals for 7-d tests were immediately exposed to the test chemical. Animals for 4-d tests were held in control water and not exposed to the test chemical until day 3. Animals were fed daily and solutions were changed on Mondays and Wednesdays. Chemical concentrations were measured by appropriate analytical techniques during each test. Survival and mean total young per female were used to compare the relative sensitivity of the 4-d and 7-d tests. Data were analyzed using traditional hypothesis testing techniques to determine chronic values from the no-observed- and lowest-observed-effect concentrations. In addition, data were analyzed using a nonparametric, monotonic smoothing technique to determine interpolated point estimates and 95% confidence intervals for the 50% inhibition concentration (IC50). Comparisons between the 4-d test versus the 7-d test for both methods of data analysis indicated that the 4-d test provides an acceptable level of sensitivity in the toxicity testing of single compounds.