Meet The Jellies

Jellyfish have been around for over 500 million years and live in any body of water. There are 10 different types of jellyfish, some as small 25mm wide with a 5mm bell and four 1 meter stingers; the largest has a 2.5 meter with eight clusters of sticky tentacles and every cluster has 100 tentacles that are 30 meters long. They consume plankton, fish eggs, crustaceans, small fish and even other jellyfish. Using their tentacle stingers as a fishnet to catch their prey then absorbing all the nutrients from the prey. The tentacles of a jellyfish is filled with millions of nematocysts that sends venom into the skin of whatever it gets into contact with. 

Jellyfish evolve from a larva into a polyp then a medusa. These stages of evolution vary in time depending on the species of jellyfish. The Immortal Jellyfish has the ability to revert to its polyp state after it has sexually matured. It is the only animal that can conduct this process of reverting completely back to it's polyp state. All jellyfish reproduce according to light, this usually occurs during either dusk or dawn.

http://kids.nationalgeographic.com/kids/animals/creaturefeature/jellyfish/
http://www.immortal-jellyfish.com/Immortal-Jellyfish-Facts.html
http://marinelife.about.com/od/invertebrates/p/Lions-mane-jellyfish-profile.htm
http://science.howstuffworks.com/zoology/marine-life/jellyfish.htm