Assessing the spermiotoxicity of butyltin compounds (TBT and DBT) in the sea urchin Paracentrotus lividus Lmk

Despite legislative restrictions about the use of paints containing organotins introduced in Europe at the end of the ’80, contamination levels in marine coastal environment are still relevant and represent a cause of concern for aquatic life. In the present study, the spermiotoxic effects of tributyltin (TBT) and dibutyltin (DBT) were assessed in the sea urchin Paracentrotus lividus. A series of preliminary experiments were performed in order to determine the appropriate sperm:egg ratio for this species which allows to enhance the sensitivity of the test. As indicated by various standard protocols for other species, we chose the lowest sperm:egg ratio (1250:1) giving a fertilisation success of approximately 90%. For each compound, six replicated experiments were carried out at concentrations ranging from 0.01 to 10 lg/l for TBT, and from 0.5 to 20 lg/l for DBT. A significant reduction of fertilisation was observed from 0.1 lg TBT/l (p<0.05); with respect to controls, the fertilised eggs were 48% at 1 lg TBT/l and 0.75% at 10 lg TBT/l. As for DBT, the lowest concentration tested (0.5 lg DBT/l) caused a slight but significant reduction in the percentage of fertilised eggs (p < 0.05) that fell to 86% at 1 lg DBT/l and to 7% at the highest concentration tested (20 lg DBT/l). Spermiotoxic effects were demonstrated at environmentally realistic levels for both compounds, the higher toxicity of TBT being confirmed. Nevertheless, with reference to our previous studies, TBT and DBT exhibited higher embryotoxic than spermiotoxic effects.