Embryonic development assay with Daphnia magna: application to toxicity ofaniline derivatives

An assay system using Daphnia magna embryos was applied to investigate the adverse effects of aniline derivatives. The data were compared with our pre vious data for chlorophenols. This new assay provides useful information to evaluate the toxicity of chemicals and the differences in sensitivity betw een the life stages. The effects of 15 aniline derivatives on embryonic dev elopment of D. magna embryos were determined. At the start of exposure, 2-6 -h old eggs (between stages 1 and 2, round in shape, diameter approx. 400 p m), were used. In control and solvent control groups, embryonic development from an egg to a free-swimming animal proceeded completely within 3 days w ith more than 90% hatchability. Median effective concentrations (EC(50)s) t o reduce the numbers hatched were determined and gross morphological abnorm alities of hatched animals recorded. Anilines induced no obvious morphologi cal abnormalities and no developmental delay although premature deaths occu rred. However, they affected the number of embryos hatching in a dose-depen dent manner. In addition, this embryo assay was more sensitive to aniline d erivatives (except for aniline) than acute juveniles immobilization assay. Ratios of 48-h EC50 (juvenile)/3-day EC50 (embryo) for eight anilines were greater than 5.0. Particularly, the ratios of 4-methyl-, 4-ethyl- and 3-met hylaniline were 77, 23 and 11, respectively. EC(50)s for embryos and juveni les were poorly correlated (r = 0.41). This indicated that the sensitivitie s of the two life stages were different to the effects of anilines. EC(50)s were poorly correlated (r = -0.097) with the log K-ow (1-octanol/water par tition coefficient). These results were compared with previous results for phenols. (C) 2001 Elsevier Science Ltd. All rights reserved.