On 17 November 2012 a specimen of the nudibranch Aeolidiella alderi (Cocks, 1852) was found for the first time in the Netherlands near Burghsluis (province of Zeeland). Since then the species was encountered quite frequently in the Oosterschelde estuary which suggests that a population has settled there. It is presumed that man played a role in the introduction of this sea slug to the Netherlands