Jelly fish

Description:

Jellyfish or jellies are the major non-polyp form of individuals of the phylum Cnidaria. They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey. Jellyfish are found in every ocean, from the surface to the deep sea. A few jellyfish inhabit freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years,and possibly 700 million years or more, making them the oldest multi-organ animal

Habitat:

Although most jellyfish are marine animals, some inhabit freshwater. This is most common for hydromedusae (in fact many hydrozoa inhabit freshwater). The best known example is the cosmopolitan freshwater jellyfish, Craspedacusta sowerbii. It is less than an inch (2.5 cm) in diameter, colorless and does not sting. Some other jellyfish populations have also become restricted into lakes, such as Jellyfish Lake in Palau. Although what first comes to mind as the common domain of jellyfish is living well up off the ocean floor in the plankton, a few species of jellyfish are closely associated with the bottom for much of their lives (that is, they can be considered benthic). The upside-down jellyfish in the genus Cassiopea typically lie on the bottom of shallow lagoons where they sometimes pulsate gently with their umbrella top facing down. The tiny creeping jellyfish Staurocladia and Eleutheria (see section on Size, above) cannot swim and "walk" around on seaweed fronds or rocky bottoms on their tentacles. Most hydromedusae and scyphomedusae that live in coastal habitats find themselves on the bottom periodically, where they may stop swimming for awhile, and certain box jellyfish species also rest on the sea bed in shallow water.Even some deep-sea species of hydromedusae and scyphomedusae are usually collected on or near the bottom. All of the stauromedusae are found attached to either seaweed or rocky or other firm material on the bottom