AbstractBackground More than 200 Scyphozoa species have been described, but few have been properly studied regarding their chemical and genetic characteristics.Catostylus tagi, an edible Scyphozoa and the sole European Catostylidae, occurs in summer at Tagus and Sado estuaries. Neither a systematic comparison between the two Catostyluscommunities nor a chemical approach on their nematocytes had been carried out...