IMPOSEX IN NEW-ZEALAND NEOGASTROPODS

Imposex has been observed in the New Zealand neogastropod species Lepsiella scobina; Thais orbita; Haustrum haustorium; Xymene ambiguus; Taron dubius; Cominella virgata and Amalda (Baryspira) australis. Imposex occurrence in L. scobina has been studied in more detail in the Auckland region, and the sequence of imposex development described. At 3 control sites, 0% frequency of imposex was observed, but at all other sites 100% frequency of imposex was recorded. Lepsiella scobina populations in the inner Waitemata Harbour were found to be severely imposexed, and appear to be in decline. A relationship was found to exist between imposex intensity (as measured by the Vas Deferens Sequence Index) and L. scobina body burdens of hexane-extractable tin. Lepsiella scobina shows considerable potential as a bioindicator species of TBT contamination in New Zealand coastal waters, due to its acute sensitivity to TBT, intertidal occurrence, widespread distribution, high abundance, direct development and limited adult mobility.