In the present work we provide the first isolation and functional characterization of a RXR orthologue in an annelid species, the Platynereis dumerilii. Using an in vitro luciferase reporter assay we evaluated the annelid receptor ability to respond to ligand 9-cis-retinoic acid, TBT and TPT. Our results show that the annelid RXR responds to 9-cis-retinoic acid and to the organotins by activating reporter gene transcription. The findings suggest a conserved mode of action of the receptor in response to a common signaling molecule and modulation by organotin compounds between vertebrates and Lophotrochozoans. © 2017 Elsevier This work was supported by the Funda??o para a Ci?ncia e a Tecnologia (FCT) projects (PTDC/MAR/105199/2008 and EXPL/MAR/EST/1540/2012) and by Norte 2020 and FEDER (Coral - Sustainable Ocean Exploitation - Norte-01-0145-FEDER-000036). A Postdoctoral grant awarded to Raquel Ruivo (SFRH/BPD/72519/2010), a Research Technician grant awarded to In?s P?scoa (EXPL/MAR/EST/1540/2012/BTI/2013/015), and a PhD grant awarded to Ana Andr? (SFRH/BD/81243/2011) and to Ana Capit?o (SFRH/BD/90664/2012).