Long term observations on Sabella spallanzanii (Annelida, Sabellidae) in the Mar Grande of Taranto (Ionian Sea). The influence of alien species

We report 30-year observations on the abundance of the Mediterranean fan worm Sabella spallanzanii (Gmelin, 1791), and the influence on its density from the introduction of two other sabellid termophilic species, belonging to the Branchiomma genus, in the area of the Mar Grande of Taranto (Mediterranean Sea). After an initial decreasing of abundance of the autochthonous species, at present, it seems that the three species have reached an equilibrium with the dominance of S. spallanzanii