First record in the Western Mediterranean Sea of Branchiomma boholense (Grube, 1878) (Polychaeta: Sabellidae), an alien species of Indo-Pacific origin.
During the last years, the concern about the effect of alien species on native marine communities has grown. The case is especially serious in the Mediterranean Sea, where over 500 alien marine species have been recorded, many of them native to the Red Sea. These species supposedly arrived to the Mediterranean through Suez Canal and are generically named Lessepsian migrants. During a survey on the polychaete fauna of the Mar Menor littoral lagoon, in the south-eastern Spain, the presence of a dense population of Branchiomma bohalense (Grube, 1878) has been detected. It represents the most western record of this sabellid polychaete in the Mediterranean Sea and its first record for the Iberian Peninsula; however, it is locally common in the Eastern Mediterranean, where it spread from its Indo-Pacific origin. In its Spanish location, B. boholense was mostly found forming dense aggregates of specimens associated with Caulerpa prolifera meadows. Based on the newly collected material, a characterization of the species is provided; it can be distinguished from other species within the genus by the shape of its macrostylodes, which differ from adjacent stylodes in being up to four times longer, tongue-shaped and flattened instead of digitiform and cylindrical.