Imposex in muricid gastropod Thais biserialis (Mollusca: Neogastropoda: Muricidae) from Tuticorin harbour, southeast coast of India

Imposex has been reported in the muricid gastropod Thais biserialis from inside the Tuticorin port. The sex ratio departed from 1:1 and the males were dominant. The frequency of imposex in females was 35%. The Vas deferens sequence (VDS) index indicated the occurrence of initial imposex stages of 1a and 2a i.e. the development of penis and penis with closed duct. The Relative penis size (RPS) index values were less when compared to the reports elsewhere. The observation of imposex indicated the possible contamination of tributyltin (TBT), which could have leached out from antifouling paints of the ships using Tuticorin port.