First records from the Ligurian Sea of the cold water species Okenia aspersa and Doto koenneckeri (Gastropoda: Nudibranchia)

Abstract

Okenia aspersa is a north-eastern Atlantic species, only previously recorded as Okenia quadricornis from the Malta Archipelago in the Mediterranean Sea, and in juvenile forms, from Sicily and the Gulf of Naples. A second adult specimen is recorded in the present paper, which was found along the Noli Cape coast, in the western Ligurian Sea (Italy). It was found on pebbles at a depth of 10 m. In the same area, at a depth of 5.5 m, two specimens of Doto koenneckeri and three of their egg masses were found. This species, also described from Norway and Ireland, was only previously known to occur in the Mediterranean Sea off Spain and France. It is likely that the cold winter temperatures of the Ligurian Sea allowed this species to live and reproduce.

What is really out there? Review of the genus Okenia Menke, 1830 (Nudibranchia: Goniodorididae) in the Mediterranean Sea with description of two new species

“…An even more intricate situation concerns Okenia alpha taxonomy, since many new species of Okenia have been recently described [2–5, 7–13], some of these lack complete morphological descriptions [5, 12–13], and many new species still require description [14]. The validity of species identification has varied historically according to the views of different authors [2, 15–19], with cryptic or pseudocryptic species still being discovered at the beginning of the twenty-first century [7]. This makes the known distribution of previously described Okenia species uncertain, thereby creating confusion of true geographic ranges [5, 13, 18].…”