Within UHEI, the Aquatic Ecology and Toxicology Group is affiliated with the Centre for Organismal Studies (COS). The COS Heidelberg studies organismic biology beyond the borders of organizational level. Research and teaching at COS is dedicated to study organismic biology from basic molecular principles from cell biology, developmental biology, plant and animal physiology to evolution, ecology, biodiversity, systems biology and biotechnology. The Aquatic Ecology and Toxicology Group has twenty-five years of experience in aquatic toxicology, especially fish ecotoxicology. Over the years, the group has made contributions to the effects of pesticides, dioxin-like substances, endocrine disruptors, genotoxicants, teratogenic compounds and neurotoxicants in fish. Most recent projects, however, have focused on the development of alternative protocols designed to replace conventional testing schemes with intact fish, be it at the level of basal (acute) and prolonged toxicity (including teratogenicity) or at the level of more specific modes of actions such as dioxin-like action, endocrine disruption, genotoxicity or neurotoxicity.