Coelenterates or Cnidaria

moon_jelly The phylum Cnidaria known to some as Colenterates consits of hollow sack like animals with stinging tenticles, (nematocysts) and radial symmetry. Coelenterates were the earliest animals to have a digestive sack, tissues such as a mouth, nerves and tentacles. During their life time these animals go through two different phases of life, the medusa stage and the polyp stage. In the medussa stage cnidaria will reproduce sexually, while the polyp stage consists of asexual reproduction. Different classes of the animals will either spend most of their life in the medusa or polyp stage.
The picture above shows one such animal, the moon jelly. Jellyfish, Anemones, Hydroids and Corals all fall into this phylum. Jelly fish are clear or translucent passive drifters. They are opportunistic feeders, but tend to be carnivorous. Their body consits of two layers, with the gut being the only cavity. Most people think of Jellyfish as toxic dangerous animals. All cnidarians do have stinging cells, but most species of jellyfish will not harm humans. Infact the next time you get a chance touch the tantacles of a sea anemone. The sticky sensation you'll feel is the stinging cells trying to hold on to you. However don't be too reassured. Some jellyfish are extremely toxic to humans, such as the famous Portuguese man-of-war or a Cyanea capillata.

Now for your viewing pleasure:
View either a MPEG or Quicktime movie of a jellyfish in action!
(Might take a while to load, but worth it)

I'm ready to turn the page!