MARISA CORNUARIETIS (GASTROPODA, PROSOBRANCHIA) - A POTENTIAL TBT BIOINDICATOR FOR FRESH-WATER ENVIRONMENTS

The ramshorn snail Marisa cornuarietis (L., 1767) exhibits imposer (oc currence of male parts in addition to the female genital duct) under t he influence of TBT (tributyltin) in laboratory experiments and accumu lates this biocide in a time- and concentration-dependent manner. A co mparison of BCF (bioconcentration factors) demonstrates that this limn ic species accumulates more TBT than marine species. Evidence is given that TBT causes hormonal disorders which are responsible for imposer development. The testosterone/oestradiol quotient reflects the imposer development which can be described by a classification scheme differe ntiating four stages in Marisa cornuarietis. In the background of the constantly increasing organotin concentration in the limnic environmen t Marisa cornuarietis could be a well-suited bioindicator for TBT poll ution. No other limnic species with a lower threshold concentration fo r measurable TBT effects is reported within the literature.