The largest jellyfish in the world is the lion's mane jellyfish, which can grow up to 8-feet in diameter and weigh up to 330 pounds. Irukandji jellyfish are the world's smallest jellyfish; This jellyfish is less than one-tenth of an inch. One of the most common jellyfish species in the world is the moon jelly. Also known common sea jellies, Moon jelly populations are found in warm, temperate coastal regions throughout the world.
Jellyfish have four classes: Hydrozoa, Scyphozoa, Cubozoa and Staurozoa. Combined, these four jellyfish classes account for 15 orders and suborders in their taxonomy.
The Hydrozoa family of jellyfish has the most jellyfish families at eight and it features over 1,000 species.
The Scyphozoa family is known as the "true jellyfish" family, since most of its species are free-swimming fish.
Cubozoa jellyfish are more commonly called box jellyfish, due to their box-shaped medusas.
Stalking jellyfish are the common name for Staurozoa, the only jellyfish family that does not alternate between the animal's polyp and medusa stages of life.
All jellyfish belong to the Cnidaria phylum. This phylum comprises all of the wildlife that experience the polyp and/or medusa stages of life. Aside from jellyfish, Cnidarians also include sea anemones and hydras. Common physical characteristics between all Cnidarians are mouths, gastrovascular cavities -- which are used for the animals' digestion -- and tentacles. Cnidarians use tentacles to grab food. Also, the body wall -- or skin -- of Cnidarians has three layers: the epidermis, the gastrodermis -- where gastronomical activity occurs -- and a thin, non-cellular membrane, known as the mesoglea.
While Animalia genera and species vary, all wildlife share similar characteristics. Animals have internal digestive chambers and are multi-cellular. Also, all animals have the ability to move in one or more stages of their lives. Male and female genders are necessary for all animals to reproduce. Jellyfish are marine-dwelling animals, but many species in the Animalia kingdom live on land.