How Jellyfish Work

Jellyfish Summary

Jellyfish are prehistoric creatures that have inhabited oceans around the world for millions of years. Although their gelatinous bodies and graceful movements make them appear to be complex creatures, they are actually quite simple in both form and function. Jellyfish are planktons that have no bones, brain, or heart. In fact, their bodies are mostly water and have just six major parts. Jellyfish live anywhere from 3-6 months and range in size from less than an inch to over 7 feet long. Although they are not aggressive creatures by nature, jellyfish are often remembered for their nasty stinging capabilities. Jellyfish mostly use their tentacles for hunting, but will also sting in self-defense. When jellyfish sting humans, it is always done in self-defense since humans are far too large for any jellyfish to eat. But, aside from the occasional sting, there's no need to fear these water-based creatures from prehistoric times.

Top 5 Jellyfish Facts

  1. Jellyfish have been around for over 650 million years and there are thousands of different species around the world.

Learn how jellyfish work.

  1. Jellyfish are not actually fish; they are plankton that fall under the phylum Cnidaria and the class Scychozoa.

Learn more about jellyfish.

  1. Jellyfish are composed of 98% water and have only 6 major body parts:
  • epidermis
  • gastrodermis
  • mesoglea
  • gastrovascular cavity
  • orifice
  • tentacles

Learn all about jellyfish.

  1. Jellyfish have 3 major stages of development:
  • Polyps - baby jellyfish
  • Ephrae - young jellyfish
  • Medusae - adult jellyfish

Learn more about jellyfish development.

  1. Although jellyfish are not aggressive by nature, their sting is painful and sometimes dangerous. There are a number of jellyfish sting remedies, but some of the best include:
  • ammonia
  • vinegar
  • meat tenderizer
  • baking soda mixed with water
  • urine

­­Learn all about jellyfish stings.

For more information about jellyfish and related topics, check out the links below.

Related HowStuffWorks Articles

More Great Links


  • Buddin, Elizabeth. "Sea Science: Jellyfish."
  • Dock Watch: Dauphin Island Sea Lab
  • "Hope for lethal jellyfish cure." BBC News, January 31 2003.
  • Introduction to the Scyphozoa: University of California Museum of Paleontology
  • Jaques, Susan. "Swimmers Beware: Jellyfish are Everywhere! "
  • Jellies: Phantoms of the Deep." Tennessee Aquarium Newsroom.
  • "Jellyfish." Gale Encyclopedia of Science. Thomson Gale, 2001.
  • National Marine Aquarium Library
  • Nielsen, John. "Jellyfish Take Over an Over-Fished Area." All Things Considered, NPR, July 21, 2006.
  • "Nuclear Plant Struck by Jellyfish." BBC News, July 2006.
  • Parry, Richard Lloyd. "How do you tackle aninvasion of giant jellyfish? Try making sushi ." The Times, December 07, 2005.,,25689-1910322,00.html
  • Pastino, Blake de. "Giant Jellyfish Invade Japan." National Geographic News, January 19, 2006.
  • Those That Sting