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

• Adapted methodology for the micronucleus (MN) assay was successfully applied to Daphnids (Daphnia magna).
• Clear dose-dependent MN induction after 2 days-exposure, with a 2-fold MN induction in daphnids exposed to the highest concentrations of metals (Cu, Zn, Cd) and pesticide (deltamethrin).
• Daphnid model to set up a reliable test for hazard and risk assessment for aquatic genotoxicity.
• When testing the MN assay in Daphnids, it offers the possibility of using it as an alternative biological model to amphibians.

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 24 h. 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 7 d. 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.