Two Seas for One Great Diversity: Checklist of the Marine Heterobranchia (Mollusca; Gastropoda) from the Salento Peninsula (South-East Italy)

Abstract

The Salento peninsula is a portion of the Italian mainland separating two distinct Mediterranean basins, the Ionian and the Adriatic seas. Several authors have studied the marine Heterobranchia (Mollusca, Gastropoda) fauna composition living in the Ionian Sea, but to date further knowledge regarding this interesting group of mollusks is still needed. Recent studies have corroborated the peculiarity of the Mediterranean Sea showing high levels of endemism and cryptic diversity. On the other hand, marine sea slugs have been revealed to be important indicators of the marine ecosystem’s health, due to their species-specific diet that consist of a vast variety of sessile and benthic invertebrates. A baseline study of the marine Heterobranchia diversity is therefore a necessary step to reveal the hidden diversity and to monitor the possible presence of alien species. The present study shows results from approximately 600 scientific dives carried out during a nine-year period in all of the main submarine habitats of the studied area, while accounting for the marine Heterobranchia from both the Ionian and Adriatic Seas. With this contribution, the list of marine Heterobranchia inhabiting the Salento Peninsula rises to 160. Furthermore, it also reports, for the first time, the presence of one alien species and three new records for Italian waters. Ecological notes and geographical distribution for each added species are provided together with animal iconography, consisting mainly of in situ photographs, for species identification.

The Sea Slug Doriopsilla areolata Bergh, 1880 (Mollusca, Gastropoda) in the Mediterranean Sea: Another Case of Cryptic Diversity

“…Since molecular evidence presented in this study indicates that D. areolata from the Adriatic Sea forms a separate species and considering that the first description of Bergh [27] was based on individuals from the same geographic area, it could be concluded that the species from the Adriatic Sea (the type locality of the species) must be considered, from now on, as the bona fide D. areolata. Interestingly D. areolata species seems to be geographically restricted to the Adriatic Sea since the only Doriopsilla reported to date from the nearby Ionian Sea is D. rarispinosa [65,66].…”

When morphology does not match phylogeny: The puzzling case of two sibling nudibranchs (Gastropoda)

“…In the last few years, studies on the systematics of nudibranchs have emphasized the need of an integrative approach, combining molecular and morphological data. Indeed, most often, few morphological characters are available for taxonomic identification and classification of these organisms, and the use of molecular data has been valuable to resolve their phylogenetic relationships and to unravel cryptic diversity (Furfaro et al., 2018, 2020; Martín‐Hervás et al., 2019; McCarthy et al., 2017).…”

Project “Biodiversity MARE Tricase”: A Species Inventory of the Coastal Area of Southeastern Salento (Ionian Sea, Italy)

“…For 63 of the taxa found, phenology traits were also reported. These included the presence of reproductive structures (31), the occurrence of seasonal organisms (25), and instances of reproductive behaviour (6) (Tables 1 and S1).…”

“…In the last 50 years, several species lists have been published for the area, but they were all almost exclusively limited to specific taxonomic groups (Mollusca Heterobranchia, [30,31]; shell-bearing Mollusca [32]; Porifera [26,33,34]; Hydrozoa [35]; Polychaeta [36]; Macroalgae [37]), or specific habitats (e.g, caves, [38,39]).…”