Jellyfish belong to the orders Stauromedusae, Coronatae,
Semaeostomeae and Rhizostomae. They all belong to the class Scyphozoa and live
in ever ocean or sea the world over. Some jellyfish are found in fresh water
rivers and streams. There nearly 300 different species of known jellyfish. Jellyfish
are free floating and carnivorous in nature.
Sea jellies or simply Jellies, jellyfish are not actually
fish. A group of jellyfish is referred to as a bloom. Jellyfish do not have
lungs and absorb oxygen through their very thin outer skin. They consist of a
hydrostatic skeleton, net of nerves and a multiuse organ that helps with
digestion and fluid circulation. Jellies are almost 90 percent water. They look
like a floating gelatinous umbrella.
Jellyfish feed on plankton and small fish and compete with
other fish species for available resources. Jellyfish are well known for their
ability to sting people which can be deadly in some cases. With a very short lifespan
(anywhere from a few hours to a few months) jellyfish reproduce constantly and
can be born and move around in giant swarms of 100,000 members.