Sensitivity of offspring to chronic 3,4-dichloroaniline exposure varies with maternal exposure.

Many anthropogenic pollutants are present in aquatic systems for extended periods of time. Populations in the field may be exposed to toxicants for several generations, which may affect their sensitivity to toxicants. Ceriodaphnia cf. dubia mass cultures were maintained for four generations in various concentrations of 3,4-dichoroaniline (0, 2.5, 5, 10, and 15 microg/L) and were reestablished every generation using fourth-brood neonates. Each generation, chronic toxicity tests were initiated using fourth-brood neonates from each mass culture treatment. Significantly (P < 0.05) reduced sensitivity to 3,4-dichloroaniline compared to control animals was shown by F1 offspring from mothers exposed to 15 microg/L, F2 offspring from mothers exposed to 5, 10, and 15 microg/L, F3 offspring from mothers exposed to 10 and 15 microg/L, and F4 offspring from mothers exposed to all 3,4-dichloroaniline treatments (2.5, 5, 10, and 15 microg/L). Possible explanations for the development of tolerance, and the possible implications of tolerance, are discussed.