| Organotin compounds, especially tributyltin (TBT) and triphenyltin (TPhT), are widely used as biocidal additives in antifouling paints due to their effectiveness. However, they also cause damage to non-target organisms and are regarded as the most toxic material ever deliberately introduced into the sea. TBT has been reported to induce imposex in gastropods, which means the imposition of male sexual organs such as penis and vas deferens on females. Imposex in gastropods is characterized as easy identifiability, irreversibility and particularity to organotin compound, which makes it an effective indicator to marine organotin compound pollution.From March 2000 to October 2002, 43 sites in 18 areas were located from Dalian of Liaoning province to Sanya of Hainan province, to investigate imposex in gastropod along the coast of China on a large scale for the first time. If available, thirty or more adult individuals for each species would be collected from the rocks or sands near the shipyards during low tides at each site. Additional specimens hard to sample were purchased from local markets near the sampling sites. All the specimens were observed carefully for anatomical characters under Carl Zeiss Stemi SV11 dissecting microscope first. A few of them were made for histological and SEM observation. The degree of imposex in each site was assessed using IOI (incidence of imposex index), RPSI (relative penis size index), VDSI (vas deferens section index) and SRI (sex ratio index). The samples collected from the surface water and sediments along southeast China were pretreated by the technique of headspace solid phase micro-extraction, and detected by GS-FPD for the concentration of MBT, DBT and TBT.A total of 44 species, represented by 14 families, were collected in the present investigation. Thais clavigera was the most abundant and widespread, and also it wasthe species to collect most easily. Imposex occured in 16 areas and 30 species in 8 families. The most of imposex species were from the families Muricidae (14) and Buccinidae (6). Among 30 imposex species, 21 were documented for the first time in the world. These findings indicated that imposex was widespread in the coastal waters of China.The development of penis and vas deferens showed diverse stages and types in imposex specimens. Type* was found in each stage of imposex development, and new imposex classification system was proposed in present paper based on these findings. Females in 13 species of 4 families were found to be sterile. Sterile female and abortive egg capsules were found in families Cypreaidae and Conidae for the first time. It was the first time to reveal the reasons leading to the sterilization of female and formation of abortive egg capsules in specimens with open vulva in some species such as Cantharius cecillei, which disproved the deduction that S4* was the end point of imposex development and abortive eggs would not be formed in such case.T. clavigera showed the widest range of imposex degree, with more than 90% incidence of imposex in 33 sites and sterile female in 15 sites. This indicated that T. clavigera was very sensitive to organotin compound pollution and imposex in gastropods was very severe in the coastal waters of China. Nevertheless, no evidence could prove that extinction of population had happened in specific area due to imposex.Imposex was closely related to shipping activities by comparing the degree of imposex in different sites. Large vessels were the main source of pollution and fishers also could induce imposex in local areas.The results indicated that organotin compound pollution was very widespread in southeast coastal waters of China by detecting the concentration of organotin compound in the surface water and sediments. The degree of imposex in T. clavigera was significantly relative to the concentration of TBT in the surface water. This indicated that imposex in marine gastropods was induced by organotin compound pollution and imposex in T. clavigera could be used as the indicator to monit... |
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