On Wednesday, 22 January, in the splendid setting of the Regional Museum of Natural Sciences, a meeting was held with Nicola Nurra — marine biologist, Scientific Diver, writer, president and founding member of Pelagosphera — entitled “Mediterranean killers – A sea under siege.” Starting from the climate crisis already underway, especially following the exceedance of the 1.5°C average temperature threshold reported by the Copernicus Global Climate Report, and moving through the drivers that are causing change in the Mediterranean Sea to occur even more rapidly, the meeting addressed alien species — some of them invasive — that have made the Mare nostrum their new home. Among the many examples discussed were Haplosporidum pinnae, the protozoan that caused the 2018 Mass Mortality Event of Pinna nobilis , and Callinectes sapidus, better known as the blue crab, which is putting at risk the farming of — coincidentally — another alien species, Ruditapes philippinarum, the Manila clam.