Sea anemones are small marine animals with a tubular body and circles of tentacles. Members of the coelenterate phylum, they are different from sea urchins which have a hard shell and long spines. Armed with stinging cells, the tentacles allow the anemone to paralyze small swimming animals which are then pushed into its mouth.
Sea anemones were one of the first creatures to appear on the earth. They are like jellyfish that have remained attached to a surface. Sea anemones are somewhat like coral expect they are bigger and live as live solitary somewhat mobile polyps rather than as part of a fixed colony. Like coral, sea anemones receive energy from single-celled plants within their tissues called zooxanthellae. The plants need nitrogen to survive.
Sea anemones take in oxygen and expel and carbon dioxide. They reproduce by dividing into two pieces (fission), by budding and by eggs. Eggs and sperms are formed in partitions in the body cavity and ejected through the mouth. The eggs are fertilized by sperm in the water. The fertilized egg develops into free-swimming larvae which develops into an anemone. Sometimes a piece of sea anemone can grow into a new animal.