TRIBUTYLTIN BIOMONITORING USING PROSOBRANCHS AS SENTINEL ORGANISMS

Tributyltin (TBT) compounds, some of the most toxic xenobiotics, produ ce a variety of pathological reactions in animals. A reliable biomonit oring method to assess the degree of environmental TBT pollution has b een described based on investigations of virilization phenomena in pro sobranch snails (Mollusca: Gastropoda). Examples are the imposer pheno menon in marine and freshwater species, the intersex reaction in litto rinids and the reduction of female sexual glands and offspring numbers in further species resulting mainly in a sterilization of females. Th e degree of imposer or intersex in populations is determined by differ ent biomonitoring indices which allow to assess the TBT pollution of t he environment at low costs with high precision. The effectiveness of TBT legislations is analysed by extensive surveys in France and Irelan d indicating that there is still a continuing threat to sensitive mari ne organisms. TBT disturbs the biosynthesis of steroid hormones on the level of estrogen biosynthesis. The observed virilization phenomena s eem due to an inhibition of the cytochrome P-450 dependent aromatase b y this organotin compound.