No longer so common: findings of Calliopaea bellula d’Orbigny 1837 (Gastropoda: Sacoglossa) and Tayuva lilacina (A. Gould 1852) (Gastropoda: Nudibranchia) along the central-eastern coast of Sicily (Ionian Sea)

The present note documents the finding of two species of marine heterobranch seaslugs along the central-eastern coast of Sicily (Italy, central Mediterranean): the sacoglossan Calliopaea bellula and the nudibranch Tayuva lilacina. These two species show a wide geographical range (C. bellula is present from Norway to the Black Sea, while T. lilacina is a cosmopolitan species) and in the literature were considered common species. However, in the last years, the number of findings of these species is decreasing, at least in the Western Ionian Sea, an area where these species seem to be currently rare. As documented for other Mediterranean areas, the reason for this decline in the number of marine heterobranch species might be attributable to a change in the current regime or to an increase in anthropogenic impacts around the coastal areas.