The micronucleus assay in the zebra mussel, Dreissena polymorpha, to in situ monitor genotoxicity in freshwater environments

Caged zebra mussels, Dreissena polymorpha, were transplanted to 6 monitoring sites receiving industrial effluents suspected of containing genotoxic chemicals. After a residence time of 2 months, the induction of micronuclei (MN) in haemocytes was determined as a criterion for genetic damage. The mean MN frequencies observed in mussels exposed to effluents ranged between 5.0 and 8.8‰. These rates were significantly higher than the baseline level of 2.0‰ recorded in a concurrent control mussel group reintroduced at the reference location. Biological fitness descriptors (mortality, attachment biotest, condition index, gonadic index) revealed no relationship between the general well-being of the mussels exposed under contrasted environmental conditions and the frequency of MN induced in their haemocytes. The biological feasibility of the transfer technique of zebra mussels, together with a moderate, but significant, inducibility of MN, are major features towards the development of a first tool for in situ monitoring of genotoxicity in freshwater environments using a common indicator species.