Imposex of Thais clavigera and Cantharus cecillei in the coastal waters of Xiamen

The degree of imposex, i. e. the imposition of male characteristics onto females, in neogastropods can be used as a sensitive and accurate biomarker to evaluate organotin contamination in coastal marine environment. Now, the imposex status in females of Thais clavigera and Cantharus cecillei in 17 sites was investigated to evaluate the organotin contamination along Xiamen Bay during 2006 and 2007. The four indices including incidence of imposex( IOI ) , relative penis size index (RPSI) , vas deferens sequences index(VDSI) and sex ratio index(SRI) were used comprehensively to assess the imposex status in order to ascertain the extent of organotin bioavailability in Xiamen Bay. Based on this research, T. clavigera in 5 sites and C. cecillei in all survey sites exhibited the IOI of 100%. At Bao ZhuYu Islet, the imposex level was the most serious with maximum VDSI value of 4. In general, the imposex level decreased from the inner to the outer of Xiamen Western Harbour, and the populations in the open Xiamen Eastern Waters including Bai Cheng, Convention and Exhibiton Center and Dadeng Island showed a lower imposex level. These results were accordant with the concentrations of organotins in 2005. The imposex degree also increased with increasing organotin contamination and decreasing distance from shipping facilities.