IMPOSEX AND ORGANOTIN COMPOUNDS IN THAIS-CLAVIGERA AND T-BRONNI IN JAPAN

Rates of occurrence and degrees of imposex, and tissue concentrations of organotin compounds (tributyltin, TBT; dibutyltin DBT; butyltin MBT; triphenyltin TPT; diphenyltin DPT; and phenyltin, MPT) in the rock shell, Thais clavigera and T. bronni (Mollusca: Gastropoda) were investigated at 32 sites in Japan from May 1990 to October 1992. The rate of occurrence of imposex was 100% in both species, at almost all sites surveyed. Degrees of imposex indicated by relative penis length (RPL) index reflected the pollution levels not only of TBT, but also TPT. In heavily polluted areas, many individuals were found with oviducts which were blocked by vas deferens development, and capsule glands which were filled with aborted egg masses. These organisms were thought to be sterile. Tributyltin and TPT concentrations in both species of molluscs were higher than those previously reported in fish and shellfish. Tributyltin and TPT concentrations were generally higher in females than in males, for both species. This suggests that female reproductive organs may have high concentrations of TBT and TPT. Estimated levels of TBT inducing imposex were 10-20 ng g-1 wet tissue for both species. As strong positive correlations between TBT and TPT concentrations were found in both species (r=0.857-0.966), the relationship between TPT concentration in tissue and RPL index was very similar to that for TBT. It is possible that TTT as well as TBT is related to induction or development of imposex in these species.