The Mediterranean Sea is known to be a hot spot for marine biodiversity, especially if considering the highly specialized Heterobranchia mollusks. In recent years, there has been increasing effort to fill some knowledge gaps existing on Mediterranean heterobranch diversity, but, to date, several potentially interesting habitats remain unexplored. In fact, most studies have been focused on sea slugs inhabiting coastal areas and lakes, but those living in extremely variable areas like Mediterranean rocky tide pools remain almost completely ignored even if it is reported worldwide that they can host a high sea slug diversity. In this context, the rocky tide pool system near the ‘Passetto’ urban beach (Ancona, Italy) in the North Adriatic Sea (Mediterranean Sea) represents a biodiversity hot spot, highlighting the importance of the conservation of this peculiar habitat. A preliminary quantitative survey on the associated Heterobranchia unveiled a thriving community residing in this limited and fragile habitat, and it inspired a more detailed investigation as performed in the present study. In order to reveal the presence of species that have gone unnoticed, an in-depth study was carried out between 2018 and 2022, which aimed to amplify the knowledge on this vulnerable environment and the fauna associated with this as yet poorly known habitat. Tide pooling activities corroborated by photographic analyses allowed the recording of 45 taxa in total and the addition of 25 species to the previously known list. Within those, (i) two species were potentially new to science, (ii) one was recorded in the Mediterranean Sea for the first time, (iii) two species were added to the Italian fauna, and (iv) one species constituted a new record for Sector 9 of the Italian Seas.

The Mediterranean Sea is considered a hotspot of molluscan diversity even if many marine environments are still poorly explored and could mask rare and/or neglected diversity. During a night survey in a rocky tide pool in the Adriatic Sea, near Ancona, Italy, Caliphylla mediterranea A. Costa, 1867, a rare sacog‑ lossan mollusc, was observed and documented. This finding constitutes the first record of this species for the Adriatic Sea and one of the few for the whole Mediterranean basin extending the known distributional range of this poorly known species.

The Levantine Basin is the first region of the Mediterranean Sea to be impacted by climate warming and the arrival of non-indigenous species (NIS) via the Suez Canal. Although Levantine zooplankton has been studied previously, recent datasets capable of detecting the occurrence of new taxa, or shifts in community composition, especially in the easternmost part of the basin, are lacking. The present study provides updated information on zooplankton composition from Tyre (South Lebanon). In this study, the occurrence of two copepod families (Canuellidae, Longipediidae) and the first regional record of Facetotecta (Y-nauplii) are reported for the first time in the Levantine Basin. Additionally, although six Calanoida species were recorded as new to the Lebanese fauna, none can be attributed to Lessepsian NIS.

Annelids are widely recognized as a major taxonomic and functional component of marine benthic systems. With more than 20,000 species formally described and a comparable number likely awaiting desc...