Is the Portuguese man o war a jellyfish?
Dr Anjani Ganase looks at jellyfish and their relations. Jellyfish encompasses a broad group of animals under the group Cnidaria, which include the true jellyfish (medusozoans) that we are familiar with. However, there are many that are closely related to the jellyfish. These include hard and soft corals, sea anemones and hydrozoans (such as the Portuguese man o war), and although they are not true jellyfish, they share very similar ecological functions and lifestyles. The life cycle of Cnidaria includes a drifting phase in the open ocean, as well as a sedentary phase connected to the seafloor. Within the different groups in the Cnidaria phylum, the time spent between the different phases can vary considerably, and some phases are even lost. Adult jellyfish release sperm and eggs into the water column to form fertilized eggs or larvae. The larvae seek to settle on a surface or the seafloor as polyps and then continue to grow and develop. While a coral will live in one sp...