Experimental designs to assess endocrine disrupting effects in invertebrates. A review

In order to gain basic understanding of the ecological effects of vertebrate Endocrine Disrupting Chemicals (EDCs), many research groups are currently testing these chemicals using aquatic invertebrates. Small crustaceans, such as cladocerans and copepods, are of particular interest since they are ecologically important and their short life cycles allow obtaining information on demographic parameters. Despite the existence of diverse literature on the development, growth and reproductive effects of EDCs on these crustaceans, only a few studies have unambiguously assessed a truly endocrine disrupting effect. This review discusses new experimental designs to differentiate between endocrine disruption and other causes of reproductive and developmental impairment. Our findings clearly illustrate that many studies may have falsely concluded that chemicals have endocrine disrupting modes of action when in fact a much simpler explanation was not previously ruled out (e.g., egg mortality, feeding inhibition). This means that there is an urgent need for integration of toxic effects on energy intake to toxicity assessments. Such an approach would permit different ectotoxicological models of action, including endocrine disrupting effects, to be distinguished and their relative roles in the overall toxic response to be clarified.