Jellyfish are among the simplest invertebrates, animals without backbones. Their bodies are made of tissue and only a few organs.
A jellyfish is a cnidarian (or coelenterate), a phyla group that includes aquatic invertebrates like coral and sea anemones. Most jellyfish live in seawater.
Jellyfish have two “ends.” One end has the mouth and tentacles, while the other is the umbrella or bell-shaped body.
The umbrella is comprised of an outer epidermis and inner gastrodermis. The two are separated by a jellylike layer called mesoglea.
To swim, a jellyfish uses a form of water propulsion to thrust itself slowly through the water. A ring of muscles around the bottom of the umbrella open and close drawing in water and then forcing it out again; this action pushes the jellyfish forward.
Jellyfish are carnivores. They feed on fish and mollusks. Jellyfish have stinging cells in their tentacles. The sting paralyzes prey. Inside the umbrella-shaped body is a mouth. Jellyfish eat and discard waste through the mouth opening. Jellyfish have a closed gut; what comes in as food is excreted as waste through the same opening.
Jellyfish are found in both warm and cold ocean waters. They are found deep in the ocean and along coastlines as well.
The scientific name for the jellyfish is Scyphozoa.