TBT Paints and the Demise of the Dog-Whelk, Nucella Lapillus (Gastropoda)

Imposex, the development of male sex organs on the female, is initiated in the stenoglossan gastropod Nucella lapillus by tin in the tributyl fraction in sea water at concentrations below 1 ng/l. The stages in the development of imposex are described and two indices measuring the intensity of the syndrome in populations defined. Fully-developed imposex causes blockage of the oviduct, preventing release of egg capsules; this reproductive failure and concomitant lack of recruitment has led to the decline of populations to the point of extinction in areas heavily contaminated (>6-8 ng/l of TBT tin) by leachates from TBT-containing antifouling paints.