Scyphozoan and Staurozoan Cnidarians gallery

The Scyphozoa or true jellyfish are pelagic Cnidarians which swim in open water thanks to the movements of their umbrella. Staurozoa are small sedentary jellyfish that adhere to algae by an extension of the umrella. Cnidarians have a single orifice, the mouth, which is surrounded by tentacles. They are radially symmetrical animals. They are characterized by the presence of stinging cells, cnidoblasts, which allow them to neutralize their prey, hence their name (from the Greek cnid- = nettle).