Effects of tributyltin and dibutyltin on sperm motility of Mytilus galloprovincialis (Mollusca: Mytilidae)

The organotin compounds, in particular tributyltin (TBT) and dibutyltin (DBT), are classified among the most harmful xenobiotics introduced by man in the aquatic environment. Despite the several studies conducted, the mechanism of their toxic action is not still clarified. Being lipophilic substances, they interact with the phospholipid component of cell membranes, determining changes in physico-chemical properties and in the activity of membrane proteins, with serious repercussions on important cellular functions. Our research aims to investigate, through a spermiotoxicity test, the influence in vivo of TBT and DBT on the bivalve mollusc Mytilus galloprovincialis. Different concentrations of two contaminants were tested varying exposure times. The results show that exposure to contaminants causes, even at the lowest concentrations tested and after only 1 h of exposure, a total block of sperm motility that could affect reproductive success in the natural habitat of the species. This block is due to a structural alteration of the beta-tubulin, highlighted by western blotting, which undergoes proteolytic cleavage. Therefore, beta-tubulin could be used as a biomarker of effect because there are not currently other specific biomarkers for using in biomonitoring as indicators of the presence of the organotins.