Observations of ctenophore species were made in the Gulf of Trieste between 2003 and 2006. We examined native ctenophore species with special attention to representatives of the orders Lobata and Beroida, and we recorded among them two non-native ctenophores: Mnemiopsis leidyi A. Agassiz 1865 and Beroe ovata sensu Mayer, 1912. The validity of the Mediterranean species Beroe ovata is discussed. We determined that among the native species, it is not Beroe ovata but rather Beroe cucumis sensu Mayer, 1912 that occurs in the Mediterranean Sea.

Genetic and morphological analyses were used to revise historical controversies in identities of Beroe species in the southern seas of Europe. DNA analyses with ITS sequences were used to explore their phylogenetic relationships. Three species of Beroe were initially listed as occurring in the Mediterranean Sea. Recently, the specimens were often re-identified using genetic analyses, causing confusions of identity. In 1997, a non-native Beroe was introduced into the Black Sea, which established there and spread to the adjacent seas, adding more controversy and confusion to species identification in this group of comb jellies. Our revisions suggest the following systematic changes: (1) re-naming of the species from what was initially labelled as Beroe ovata, and later as B. cucumis (sensu Mayer, 1912), to Beroe pseudocucumis sp. nov.. (2) Beroe mitrata but not Beroe ‘anatoliensis’ inhabits the Aegean Sea, as was reported previously. (3) Beroe ovata is the only species of Beroidae that became invasive and should be used with the authority of Bruguière, 1789, but not in the sense of Mayer, 1912. (4) Beroe forskalii appears to be represented by two species in the Mediterranean and in the Antarctic, but further justification is needed. (5) Beroe cucumis is a species of bipolar occurrence, inhabiting both subpolar areas and its recent definition as Beroe ‘norvegica’ is incorrect.