Monitoring genotoxicity in freshwater microcrustaceans: A new application of the micronucleus assay

We have applied the micronucleus (MN) assay to the measurement of genotoxicity in microcrustaceans. Daphnids (Daphnia magna) and Copepods (Acanthocyclops robustus) were collected in situ and acclimated in the lab for 24h. The MN assay was successful with the Daphnids but not with the Copepods. Adult Daphnids were exposed to sublethal concentrations of metals (Cu, Zn, Cd) or insecticide (deltamethrin) for 2 and 7d. Dose-dependent induction of MN was observed after 2 d exposure, with 2-fold induction at the highest doses for each chemical tested. The advantages and ecological relevance of using Daphnids in genotoxicity assessment are highlighted. The Daphnid assay may be a reliable test for aquatic genotoxicity hazard/risk assessment and a useful alternative to studies of amphibians.