Reversibility of trace metals effects on sea urchin embryonic development.

The sea urchin embryo-toxicity test is widely used to assess the toxicity of contaminants and environmental matrices. In standard guideline and literature studies, the classical toxicity criteria are based on distinguishing between normal and abnormal embryos at pluteus stage. The aim of this research was to further expand the potentiality of the recently developed Integrative Toxicity Index (ITI), investigating the reversibility of the effects induced by various trace metals (cadmium, copper, lead and zinc) on sea urchin development. For this purpose, embryos were observed after different periods of exposure and recovery to metals. Results were analysed comparing ITI with standard criteria, thus moving from the simple observation of general effects to the classification of their severity. The onset and reversibility of effects by trace metals were more efficiently discriminated by the use of the ITI, which recognized and weighted the delay and degree of various abnormalities. Above, this study was expected to provide new insights into the capability of each metal to induce anomalies leading to a block or delay in embryogenesis of the embryos to recover normal development after metal exposure, thus adding further ecological value to the sea urchin bioassay.