Jellyfish are mainly free-swimming marine animals with umbrella-shaped bells and trailing tentacles, although a few are anchored to the seabed by stalks rather than being mobile. The bell can pulsate to provide propulsion for highly efficient locomotion. The tentacles are armed with stinging cells and may be used to capture prey and defend against predators. Jellyfish have a complex life cycle; the medusa is normally the sexual phase, which produces planula larva that disperse widely and enter a sedentary polyp phase before reaching sexual maturity.
Jellyfish are found all over the world, from surface waters to the deep sea.
Classification: Biota Animalia (Kingdom) Cnidaria (Phylum)
Class Cubozoa - box jellyfish
Class Hydrozoa - Hydroid
Class Scyphozoa - true jellyfish
Class Staurozoa - stalked jellyfish