Incidence of imposex in populations of Acanthina monodon (Pallas, 1744) (Mollusca: Neogastropoda) from Southern Chile under different levels of anthropogenic activity

Abstract

Imposex is the development of male sex organs in neogastropod females, a phenomenon associated with the presence of organotin compounds such as tributyltin (TBT). Here we assessed the incidence of imposex in two populations of Acanthina monodon from southern Chile with different levels of human activities. One location was chosen specifically to evaluate the increase or decrease of imposex, comparing our results with previously pub-lished data. In each site we collected 103 specimens and quantified the following indexes of imposex: percentage of females with imposex, relative penis length index (RPLI) and relative penis size index (RPSI). In Metri, where human activity is relatively important, imposex in females was 48,6%, while in Vic-toria Island, where human activity is limited, imposex was not observed. The percentage of imposex in Metri was more than eight times greater than the value reported in a previous study of 1999; the RPLI and RPSI indexes were also greater than in 1999. These results suggest an increase in the amount of the pol-lutant in the environment or a higher exposure of the snails in this locality to these compounds.