Environmental endocrine disruptors (EDC’s) are environmental contaminants that act by alteration of one or more aspects of the endocrine system of affected individuals. Though well characterized for vertebrates, the extrapolation of EDC effects information to aquatic invertebrates has been inhibited by the large differences in physiological regulatory pathways. There is a significant need for test methodology development and the identification of ‘biomarkers’ of EDC effects for aquatic invertebrates (Hutchinson and Pickford 2002).