"Jellyfish" by Dong Ma

Jellyfish are marine invertebrates belonging to the class Scyphozoa of the phylum Cnidaria. The term "jellyfish" is also applied to some close relatives of true scyphozoans, such as the Hydrozoa and the Cubozoa. They can be found in every ocean in the world and even in some fresh water. The term "jellyfish" is a common name, and therefore does not imply any systematic relationship to vertebrate fish -- jellyfish are cnidarians.
Jellyfish lack basic sensory organs and a brain, but their nervous systems and rhopalia allow them to perceive stimuli, such as light and odor, and respond quickly. They feed on small fish and zooplankton that become caught in their tentacles. Most jellyfish are passive drifters and slow swimmers. Their body parts are made up of 92%-98% water and consists of bell, stomach pouch, lappet, oral arms, tentacles, and rhopalium.
Jellyfishes are an important food source for many Asian countries. When stung by a jellyfish, first aid may be needed immediately. The stings of true Scyphozoan jellyfish are not generally deadly, though species of the completely separate phylum Cubozoa (box jellyfish) such as the famous and especially toxic Irukandji can be fatal. Jellyfish sting are often very painful and less dangerous. first aid for the uncomplicated jellyfish stings is to rinse the tentacles off with salt water. Do not use fresh water, it will worsen the stinging pain. Remove any remaining tentacles with a gloved hand or tweezers. And watch for allergic reactions. Urine will not work on a jellyfish sting. Some victims have reported pain relief, but urine does not always have enough acid to neutralize the venom. Use vinegar.

For more information go to http://en.wikipedia.org/wiki/Jellyfish :o