Imposex incidence in Hexaplex trunculus from Kaštela Bay, Adriatic Sea

Abstract

          Imposex, a pseudo-hermaphroditic condition characterized by the development of male sexual characteristics in female prosobranch gastropods, is used as a bioindicator of pollution by tributyltin (TBT) -based antifoulants. The incidence and the intensity of imposex, evaluated from the vas deferens sequence index (VDSI) and the female penis length (FPL), were investigated in Hexaplex trunculus populations from seven locations in Kaštela Bay (Adriatic Sea, Croatia). Analysis of 131 females revealed the absolute prevalence of imposex at all investigated locations. Furthermore, most of the females showed signs of advanced imposex development (VDSI=4.4±0.8, range=2-5). Female penis homologues were found to be well developed (max=20 mm) with mean values ranging from 5.2-12.6 mm. Significant differences were detected regarding both the VDSI (H=36.24, p<0.001) and the FPL (F=7.08, p<0.001) between the locations. The results presented in the study confirm the widespread incidence of imposex and can provide reference values for future monitoring programs.