| Summary: | Tributyltin (TBT) and its derivatives are widely used as antifouling paints for ships, resulting in their being released into the marine environment. Aquatic invertebrates, particularly marine gastropods, are extremely sensitive to TBT and undergo changes in the imposition of male secondary sex characteristics in response to exposure. This study aimed to evaluate the development of imposex and the expression of the retinoid X receptor (RXR) in tissues of Plicopurpura pansa (males and females) exposed to tributyltin chloride (TBTCl). The histological results showed a penis-like structure in imposexed female and an undeveloped vas deferens that lacked circular muscular layers. TBTCl treatment increased the messenger RNA (mRNA) of RXR in females with imposex. The highest level of mRNA RXR was found in the digestive gland and penis-forming area in females under in vivo exposure compared with control females. These results indicate that TBTCl modulates mRNA levels of RXR in females. mRNA RXR in imposex females and females exposed to TBTCl only was similar to that of males, indicating that RXR might contribute to the development of imposex. To our knowledge, this study is the first to show that TBTCl induces imposex and biphallia in this snail species, and that this effect is accompanied by an increase in RXR expression.
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