Cnidarians

= Cnidarians =
 * contains 9,000 species of animals found in aquatic and marine enviornments
 * Cnidarians are classified into four main groups:
 *  Anthrozoa (sea anemones,corals)
 * Schyphozoa (jellyfish);
 * Cubozoa (box jellies);
 * Hydrozoa, a diverse group that includes all the freshwater cnidarians as well as many marine forms(man-of-war)

Anthrozoas

 * do not have medusa stage in their development
 * instead,release sperm and egg that form a planula.
 * produce asexually through budding
 * include sea anemoneas and corals
 * anemones and corals live in isolation
 * however most corals from colonies form polyps

Schyphozoas

 * include "true jellyfish"
 * made of 99% water
 * have 2 life phases,including medusa and jellyfish stage.
 * range from 2-40 centimeters in diameter
 * not in freshwater
 * can be found throughout world's oceans,from surface to great depths

Cubozoas
 * box jellyfish differ from other jellyfish because they have a square umbrella instead of a round one
 * nervous system is more developed than other jellyfish
 * Their eyes are located on each of the four sides of their bell in clusters.
 * These enable them to see specific points of light,instead of just distinguishing between light and the dark.
 * have been called the "world's most venomous creature"
 * string is rarely detected until after venom is injected
 * live in Australia,Philippines,Hawaii,Vietnam and other tropical areas.

Hydrozoas
 * can be solidary or colonial
 * mostly live in saltwater
 * some include Portuguese man-of-war and the freshwater jelly
 * colonies are usually diocious, which means that they have seperate sexes. all polyps in each colony are either male or female,but not both sexes in the same colony.
 * is a very diverse class,live as polyps, medusae, and species that alternate between the two.
 * The umbrella can commonly ranges in diameter from 0.5 mm to 50 mm. but in some species the size is larger,reaching from 10-20 centimeter.
 * Portuguese Man-of-war lives on the surface of the ocean,and can be found in tropical and subtropical regions of the Pacific and Atlantic oceans.