Causes of Imposex in the Dogwhelk Nucella lapillus (L.) and its Use as a Biological Indicator of Tributyltin Contamination

Exposure to the oestrogen-mimic nonylphenol under laboratory conditions can cause imposex in dogwhelks Nucella lapillus. There were also elevated levels of imposex in N. lapillus collected from a shore adjacent to a gull roost, and from shores beneath cliffs which supported breeding colonies of seabirds. Gulls carry trematode parasites Parorchis acanthus which infect N. lapillus as intermediate hosts but, although parasites can affect the development of the genital system in gastropods, there was no relationship between levels of infestation and the severity of imposex. It is possible that, in these cases, compounds in the birds’ excreta had caused imposex. These data have implications on the use of imposex as an indicator of environmental levels of TBT.