TBT-induced imposex related to age and length in Buccinum undatum at two localities in Balsfjorden

Abstract

Background: The organotin compound tributyltin (TBT), used as an antifouling agent in ship hull paint, is known to cause imposex in several species of marine gastropods. Imposex is the imposition of male sexual characteristics on females, and can lead to female sterility. The common whelk, Buccinum undatum, is a common species in Norway and has received attention for its export potential. Because B. undatum varies geographically in reproduction and morphology it is important to study the species before exploiting the populations. No work has been done to assess imposex in the common whelk in Norway, and little is known about the species in Norway altogether. Methods: Buccinum undatum was caught at Berg and Balsnes in Balsfjord, Troms county, Northern Norway, for comparative studies of imposex and morphology. Shell length and male penis length were measured, and females were checked for imposex. Age was read by counting striae on the backside of the operculum. Sediment samples were taken at each location for analysis of TBT contents, and snails with and without imposex were also analyzed for TBT. Results: There was a significant difference in shell length between Berg and Balsnes. The whelks at Berg seemed to be longer than at Balsnes. There were no differences in incidence of imposex between the localities, nor between length groups within each locality. There seemed to be an increase in percentage of imposex with increasing age at Balsnes. No female whelks had imposex severe enough to cause sterility. TBT consentration was below detection limit in the sediments at both locations, while it was detected at low concentrations in females both with and without imposex. Conclusions: Buccinum undatum display morphological differences between close localities. TBT contamination at Berg and Balsnes is low and has low impacts on the whelk populations with respect to imposex. Imposex has no impact on reproductive abilities of the common whelk at Berg and Balsnes.