Alien travel companies: the case of two sea slugs and one bry-ozoan species in the Mediterranean Sea. Favorinus ghanensis and Polycerella emertoni in the Mediterranean Sea

Mediterranean marine fauna is constantly changing due to the entry of non-indigenous (NI) spe-cies, the speciation of new taxa and/or the loss of endemic biodiversity. In this framework, it is very important to monitor this constant change and investigate on a possible new pathways of dis-persion. Marinas and ports are considered key stations to detect and study some important eco-logical aspects such as NI/invasive species, effects of climate change and pollution. Here is reported the case of a group of NI species that presumably have reached the Mediterranean Sea all together being each of them ecologically associated to one another. The bryozoan Amathia verticillata, the sea slugs Favorinus ghanensis and Polycerella emertoni were found in the shallow waters of Fezzano’s marina, in the gulf of La Spezia (Ligurian Sea, Mediterranean Sea). Molecular analyses were carried out to exclude cryptic diversity and to investigate the phylogenetic relationships occurring be-tween closely related taxa. The spreading of these two NI sea slugs into the Mediterranean Sea was confirmed and the first record of P. emertoni from the Ligurian Sea reported. This finding sheds some light on the poorly known ecology of these species that could be useful for future monitoring and conservation strategies.