New tools and strategies for biomonitoring marine ecosystems: learning from echinoderms

Marine ecosystems are critically threatened by several anthropogenetic compounds (xenobiotics). In the last decades, among the numerous relevant xenobiotics, specific attention has been given to the Endocrine Disrupter Compounds (EDCs): these chemicals are able to alter the endocrine functions potentially causing serious health problems in humans and wildlife. In spite of the global relevance of these pollutants, most past and recent ecotoxicological research has been addressed only to a selected number of animal models, usually vertebrates, whereas invertebrates (particularly marine invertebrates) have been largely neglected. Among the scarcely considered invertebrate taxa, there are common macroinvertebrates such as echinoderms which actually are regarded as representative animals of the marine ecosystem. This contribution will explore the appropriateness of echinoderm models as test species in marine ecotoxicology. Presence and role of the different echinoderm classes in marine ecosystems will be discussed in terms of their ecological relevance and susceptibility to be targets of EDCs. Moreover, echinoderms can offer a wide range of biological processes appropriate for studies on endocrine dysfunction; although basic knowledge on echinoderm endocrinology is still scarce, several works suggested that many physiological processes of these invertebrates are plausibly regulated by humoral mechanisms, often similar to those found in vertebrates. Here, the sensitivity and responsiveness of different biological processes such as reproduction and regenerative development are discussed in relation to EDCs ecotoxicological tests on two echinoderm species: the sea urchin Paracentrotus lividus and the crinoid (feather star) Antedon mediterranea. The effects of low-dose exposures to several EDCs (triphenyltin, fenarimol, p,p'-DDE, methyltestosterone and cyproterone acetate) were investigated by several parameters including regenerative growth, histological pattern, gamete development and gonad maturation. In most of the exposure experiments, evidences of plausible endocrine disruption were found. These experiments were also considered in terms of modelling the fate of the contaminants in the aquaria. The modelling approach in the evaluation of the exposure can help in the planning phase of ecotoxicological tests, and, later, in the comprehension of the results and in the exportability to the natural environment. Finally, problems and weak points encountered with these animal models will be critically discussed together with considerations and perspectives for future research developments.