The earliest reported alien species that entered the Mediterranean after only nine years from the inauguration of the Suez Canal was "Meleagrina" sp., which was subsequently identified as the Gulf pearl-oyster, Pinctada radiata (Leach, 1814) (Bivalvia Pteriidae). Thereafter, an increasing series of records of this species followed. In fact, nowadays it can be considered a well-established species throughout the Mediterranean basin. Since the Red Sea isthmus was considered to be the only natural way of migration, nobody has ever doubted about the name to be assigned to the species, P. radiata, since this was the only Pinctada Röding, 1798 cited in literature for the Mediterranean Sea. Taxonomy of Pinctada is complicated since it lacks precise constant morphological characteristics to distinguish one species from the others. Thus, distribution and specimens location are particularly important since different species mostly live in different geographical areas. Some researchers also used a molecular phylogenetic approach, but the results were discordant. This taxonomic conundrum was reexamined this time applying morphological taxonomy. Increasing vessel traffic and records of vast amounts of Pinctada specimens with morphologically different shells led us to formulate the hypothesis that a separate Pinctada population of different geographical provenance could be present. Specimens were grouped according to the site of collection in the Mediterranean basin. Results from these morphological studies confirmed that, according to us, there were two distinct species, P. radiata and P. fucata (Gould, 1850). Morphological comments and interpretations on the taxonomical status of both species together with autoecological notes and a literature review of the molecular phylogenetic studies conducted will be here presented.

During a malacological survey we conducted at the Ionian island of Lefkada (Greece) in September 2022, we found living specimens of the following non-indigenous molluscs not yet reported for the area: Viriola cf. bayani Jousseaume, 1884, Dendostrea frons (Linné, 1758), Isognomon aff. australicus (Reeve, 1858) and Isognomon bicolor (C. B. Adams, 1845). The presence of these species indicates the spread of non indigenous marine species to this area.