Imposex in One of the World’s Busiest Shipping Zones

Tributyltin pollution from antifouling paint is well known to disrupt the endocrine system in female marine gastropods. The masculinization of females, including the aberrant growth of a penis and vas deferens and occlusion of the capsule gland, has been reported primarily in neogastropods and is particularly well documented in muricids. Compared to temperate areas, few studies of imposex have been undertaken in the tropics, and there are few studies in general on non-neogastropods. Here we report a high frequency of imposex near the Pacifi c mouth of the Panama Canal in two species of muricids and two species of calyptraeids. The frequency of imposex declined rapidly with distance away from the canal, and several species appeared to be mostly normal less than 10 km from the entrance. This is the fi rst report of imposex in Acanthais brevidentata, Thaisella kiosquiformis, Bostrycapulus calyptraeformis, Crepidula cf. nivea, and Anachis fl uctuata. Because imposex has not previously been reported for the Calyptraeidae, a family of protandrous gastropods, a laboratory study was conducted to verify that imposex was not simply retention of the penis after sex change. The 2007 ratifi cation of the International Maritime Organization’s convention on antifouling systems should reduce the levels of TBT worldwide, but the persistence of this compound in sediments suggests that imposex may continue to be a problem at the mouth of the canal as routine dredging and large tides frequently resuspend sediment.