First record of the alien gastropod Melibe fimbriata (Opistobranchia: Tethyidae) in the Taranto seas (Mediterranean Sea).

The first occurrence of Melibe fimbriata in the Taranto marine coastal area is reported. This mollusc was observed on muddy bottoms covered with dense algal beds mainly composed by Chaetomorpha linum, Gracilaria spp. and the invasive chlorophyta Caulerpa racemosa. Occasionally, M. fimbriata specimens were found in proximity of mussel farms. Most specimens of M. fimbriata were observed during diurnal foraging activity and associated with anaspideans species, like native Aplysia depilans and lessepsian immigrant Bursatella leachii. M. fimbriata can be considered a definitively resident species in the opistobranch fauna of the Taranto seas