The occurrence of the alien species Polydora cornuta Bosc, 1802 (Polychaeta: Spionidae) in North Adriatic lagoons: an overlooked presence

Abstract The alien polychaete Polydora cornuta was found in Venice, Marinetta and Barbamarco lagoons (north-western Adriatic Sea). Reproductive specimens were collected from all the above-mentioned lagoons at different sampling times, showing the presence of established populations. The highest recorded population density of this species was 2880 ind. m–2. Data on adult morphology, reproductive traits and early stage larval morphology are provided. An examination of old samples revealed the presence of this species in Italian waters at least since 2009, and maybe even as far back as the early 1990s. The identity of P. cornuta may have been concealed for a long time because of taxonomic confusion with P. ciliata. Previous records of this species were recently published for the western Mediterranean Sea, on the Turkish and Greek Aegean coasts. The present paper extends the geographical distribution of P. cornuta to the Adriatic Sea and adds a new record to the list of alien species in the Italian waters.