Cnidarians
Even though cnidarians are beautiful creatures, many people are afraid of them. Why? Because they have small stinging cells call cnidocytes on each of their tentacles. Cnidocytes are used to capture food and to use against predators. The cnidocyte cells contain poison arrows that are connected to threads called nematocysts. If, for example, a small fish touches a tentacle, the poison arrow shoots out to paralyzes the prey. Then, the tentacle will bring the prey to its mouth and into the cnidarian's simple digestive cavity. After the prey has been digested inside of the hollow sack, the food will pass into the body cells and the waste must go back out of the mouth because the cnidarians only have one opening inside of them, so that hole is the mouth and the anus.
The Cnidarians have two different body forms, polyp form and medusa form. Polyp form is when the cnidarian doesn't really move around and sits on the ocean floor with its tentacles and mouth pointing upward. Some examples of polyps are hydras, corals, and sea anemones. The medusa form is sort of like an umbrella. The medusa body plan can swim and move about, with its tentacles and mouth facing downward, like a jellyfish. -hr
The Cnidarians have two different body forms, polyp form and medusa form. Polyp form is when the cnidarian doesn't really move around and sits on the ocean floor with its tentacles and mouth pointing upward. Some examples of polyps are hydras, corals, and sea anemones. The medusa form is sort of like an umbrella. The medusa body plan can swim and move about, with its tentacles and mouth facing downward, like a jellyfish. -hr