Medusozoans reported in Portugal and its ecological and economical relevance

Cnidaria is a phylum of predominantly marine organisms that evolved into two basic body forms: “polyp” characterized by a tubular body; and “medusa” the free-floating stage characterized by a bell-shaped body. A fast increase in the abundance of the free-living stage of cnidarians known as “jellyfish”, can produce huge impacts on fisheries, public health, tourism, and the normal functioning of factories and aquaculture. Those mass occurrence events are influenced by some natural factors such as water temperature, wind and water tides, but also induced by global warming, overfishing, eutrophication and widening of invasive species habitats. These events have also been reported in the Portuguese coast, but the information is still scarce and therefore their impacts are underestimated. Herein, we provide an updated list of medusozoans in mainland Portugal and archipelagos, and their available genetic information. The data gathered showed a total of 272 medusozoans species comprising 254 hydrozoans, 15 scyphozoans, 2 staurozoans, and 1 cubozoan. The data compiled revealed that 26 % of the reported species did not present any genetic information in public databases (May 2019). Moreover, most of these sequences belonged to the mitochondrial markers 16S ribosomal RNA (16S rRNA) and cytochrome c oxidase subunit I (COX1), and to nuclear markers 18S ribosomal RNA (18S rRNA) and 28S ribosomal RNA (28S rRNA). However, the behavior of the medusozoans registered revealed that the hydrozoans Blackfordia virginica, Physalia physalis, Velella velella and the scyphozoans Aurelia aurita, Catostylus tagi, Pelagia noctiluca and Rhizostoma luteum can produce mass occurrence events. Hence, far more than an updated list of medusozoans species in Portugal, and their genetic information, we revealed the species of medusae more capable of provoking events of mass occurrence that could suddenly affect the dynamic of the ecosystems.