Jellyfish are part of the Kingdom Animalia. All Cnidaria are within the invertebrate portion of the Kingdom Animalia, which consists of over 97% of invertebrates. All invertebrates do not have backbones as well as many other similar characteristics. They all are multicellular and have no cell walls. Most invertebrates have tissues, except sponges, and most reproduce sexually. Also, Most invertebrates are symmetrical. Invertebrates are heterotrophic which means they have to hunt for food, they cannot produce it themselves.

This is a Lion's Mane jelly.

Image From The Oceanic Research Group

Image From The Oceanic Research Center

 

In Phylum Cnidaria there are Jellyfish, sea anemones and coral. Cnidaria means “to sting”, which many Cnidaria live up to that name. Cnidarians have radial symmetry, which means that similar body parts are arranged around a central axis, which causes there to be no front or back. There are two forms of Cnidaria, the polyp and the medusa. A polyp is typically attached to something and is more cylindrically shaped. For example, coral and sea anemones are polyps. The medusa is the free-swimming cnidarians, which are bell shaped. They have no true nervous system, but they do have a nerve net. There is only one opening for the digestive system that opens into the gut. There are two true layers the epidermis, the outer layer, and the gastrodermis, the internal layer. Mesoglea is the layer between the other two layers.

Jellyfish live in all oceans. Some live in fresh water, but that is only a few species.