Tributyltin (TBT)-induced imposex in the Neogastropod Hexaplex trunculus in Italian coastal waters: morphological aspects and ecological implications

Neogastropod snails are gonochorist, i.e. the sexes are separate, but when exposed to tributyltin, a biocide used in marine antifouling paints, the fe male becomes masculinized, typicality developing a penis and a vas deferens . This process is termed 'imposex' (describing a superimposition of male se x organs onto the female) and the phenomenon has been recorded in many spec ies world-wide. Evidence suggests it is caused by an hormonal imbalance ind uced by tributyltin at a very low ambient concentration of just a few nanog rams per litre. Thus, imposer can be used as a highly sensitive bioindicato r of tributyltin pollution, especially as the degree of its development app ears to be dose-dependent. In the Mediterranean, only Hexaplex trunculus (M uricidae) has been studied in this context, but information is limited and the status of H. trunculus populations along the Italian coast remain to be investigated in detail. The present survey is based on examinations of nea rly 3000 specimens collected at various localities around Italy. The develo pment of imposer in H. trunculus is described and its ecological implicatio ns for the species are discussed.