Genomic Response in Daphnia to Chemical Pollutants

Chemicals released into the environment have a potential to affect on various species and evaluation of the impacts on ecosystems including aquatic organisms is urgent issue. In order to evaluate chemical effects on various species, it is important to understand their mode of action. Recent advances in toxicogenomics, the integration of genomics into toxicology is promising for understanding mode of action in responding to chemical pollutants. In this study, we applied the toxicogenomics to an aquatic organism, Daphnia magna. Among aquatic organisms, Daphnia magna has been used extensively in acute toxicity or reproductive toxicity tests. Although these types of tests can provide information on hazardous concentrations of chemicals, they provide no information about their mode of action. Thus we developed an oligonucleotide-based DNA microarray based on a Daphnia expressed sequence tag (EST) database and applied for ecotoxicogenomic assessment of Daphnia magna. The DNA microarray was used to examine gene expression profiles of neonate daphnids exposed to several different chemicals. Exposure to these chemicals resulted in characteristic gene expression patterns that were chemicalspecific. This result indicates that our newly developed DNA microarray can be useful for a mechanistic understanding of chemical toxicity on a common freshwater organism, Daphnia magna, and that the Daphnia genomics is useful for aquatic ecotoxicology.