The imposex incidence was appraised in South American gastropods, considering the scenario before and after the global ban of tributyltin (TBT). A statistically significant reduction in imposex indexes was observed in Stramonita haemastoma collected in 2006 and 2010 from areas under the influence of four coastal harbors from southern Brazil. This reduction may be because of the effectiveness of the global ban issued by the International Maritime Organization, although the restrictions on TBT-based antifouling paints in Brazil might also have helped. Even so, a residual organotin contamination was still detected in female tissues (levels ranged from 7.6 to 164.9 ng Sn/g for TBT; from <2 to 214.5 ng Sn/g for dibutyltin; from <3.5 to 178.8 ng Sn/g for monobutyltin; and from <1.5 to 53 ng Sn/g for triphenyltin). Thus, although a reduction in imposex and environmental levels of organotins is expected in every ocean worldwide soon after the implementation of national and international restriction regulations, this will depend on the effectiveness of the global TBT ban; the effectiveness of local restrictions on producing, selling, and using TBT-based antifouling paints; and specific characteristics of local sediments, because metabolization rates and sorption/desorption of TBT previously deposited might affect its environmental bioavailability. Therefore, the reduction trend detected in the present study cannot be extrapolated to other Brazilian or South American coastal areas.

Imposex incidence, organotin tissue levels, and sex steroid (free and esterified testosterone and estradiol) levels were assessed in Stramonita haemastoma from Babitonga Bay (Santa Catarina State, Southern Brazil). The imposex levels showed a reduction when compared to a previous evaluation performed in the same area. In spite of that, the detected imposex incidence indicated the occurrence of tributyltin (TBT) inputs that were still able to produce endocrine disruption in local gastropods. In addition, a high level of organotins was observed in tissues of imposexed females. These females also showed a hormonal imbalance, especially in the total testosterone/total estradiol ratio. These findings obtained under realistic field conditions suggest that the steroid pathway could be responsible by the imposex induction after exposure to TBT. In this case, measurements of sex steroid levels can be an additional evidence for monitoring sites and impose affected gastropod populations.

No abstract

400 adult individuals of the Stramonita haemastoma were collected from a pristine beach in Ceara State, Brazil. These organisms were transplanted into a marina with intense shipping activities and were fed weekly with oysters obtained from the same beach from which they were collected, being exposed only to the bioavailable organotins in the environment, without accounting for diet (waterborne exposure). 30 individuals were analyzed every 2 weeks after transplantation to investigate the development of imposex. After 15 days, 90% of the females had developed imposex (VDSI I-III, RPLI 3.22), with 100% of the females developing imposex after 30 days; at the end of the experiment, the VDSI levels ranged between I-V. These results were compared with those of a previously published study performed simultaneously in which gastropods obtained in same area were fed in the laboratory with oysters from the same marina in which the gastropods were transplanted (dietborne exposure). Despite the higher levels obtained through exposure via water at the end of 90 days, both exposure routes induced imposex in 100% of the females of the S. haemastoma. However, aqueous exposure induced higher levels, possibly due to the constant contact between the organisms and contaminants.