In the present paper, the semelid Theora lubrica is recorded for the first time in the Atlantic Ocean, based on numerous specimens collected in the Nervión Estuary and Pasajes Port (Basque coast, south-eastern Bay of Biscay). This species is native to Japan and the Pacific coast of Asia, and has previously been introduced to other areas outside its natural range. Its presence in ports or adjacent areas, suggests that the shipping activity is the most likely pathway of introduction of this alien species in the new settlements. On the Basque coast, the possible impact of T. lubrica on native communities is still uncertain. Future surveys will help us to evaluate its introduction.
