Tributyltin (TBT) effects on Ocinebrina aciculata (Gastropoda: Muricidae): imposex development, sterilization, sex change and population decline

The anatomy and histology of the male and female genital systems of the prosobranch Ocinebrina aciculata are described and compared with Nucella lapillus and Ocenebra erinacea. O. aciculata, collected at Roscoff (France) from 1989 to 1993, exhibited imposex (pseudohermaphroditism; occurrence of male parts in addition to the female genital duct) in response to tributyltin (TBT) pollution. Two stages of imposex development (4 and 5) with three different types (a, b, c) in stage 5 can be distinguished and are documented for the first time with scanning electron micrographs. Furthermore, three additional alterations of the genital tract are shown. Evidence for TBT-induced sterilization and protogyne sex change is given. This species exhibits a higher TBT-sensitivity than Nucella lapillus, the most sensitive TBT indicator species known previously. Due to TBT pollution, populations of Ocinebrina aciculata are declining in France and corresponding symptoms for this extremely endangered species are described: high numbers of sterilized females, male-biased sex ratios and poor reproductive performance and recruitment. The question of whether chemicals in the environment can influence the hormonal systems of humans and animals has been discussed for many years. At the centre of interest from early on were compounds with a known or supposed estrogenic activity and their possible impact on male reproductive health. However, another class of endocrine disruptors, environmental androgens such as TBT with their detrimental effects on females, may also cause serious problems for wildlife and for mankind.