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Jellyfish Facts: Everything You Need To Know About Jellyfish!

Facts About Jellyfish: What are Jellyfish?

Jellyfish are gelatinous zooplankton from the Phylum Cnidaria. From an anatomical standpoint they are little more than a sac within a sac. Their body composition is 95% water. They do not have a brain, or even a central nervous system. They lack anything that remotely resembles a skeletal system. Most jellyfish do not even have eyes. Aside from eating, their only interaction with their immediate surroundings is the ability to distinguish between up and down, light from dark, or physical contact. Yet somehow their light sensory abilities allow them to perceive and maneuver around foreign objects.

jellyfish diagram

Facts About Jellyfish: How Old are Jellyfish?

jellyfish fossil
Watch Living Fossils

Jellyfish are one of the oldest non-extinct life forms in existence. This should come as little surprise considering they are just one step up the evolutionary ladder from single cell organisms. Jellyfish fossils have been unearthed dating as far back as the Cambrian Period some 600 million years ago. The Cambrian Period predates not only the extinction of dinosaurs but their existence itself. These mysterious creatures will probably be swimming the Earth’s oceans long after mankind is gone.

Facts About Jellyfish: Can You Keep Jellyfish as Pets?

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desktop jellyfish fish tank aquarium, for moon jellyfish
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Keeping jellyfish as pets is a new concept in the home aquarium industry. It was, after all, only two decades ago that jellyfish were first exhibited in a public aquarium. Until then even the most knowledgeable experts didn't know enough about jellyfish to keep them alive in captivity.  You can’t just walk into your local pet shop and buy a pet jellyfish aquarium. You can’t order a jellyfish from even the largest online fish suppliers. The idea of keeping jellyfish as pets falls, at least for the moment, in the realm of specialty items. This is probably because jellyfish require an aquarium that was specifically designed to keep these fragile organisms alive and healthy.  There is currently only a single company that produces an affordable desktop jellyfish aquarium fish tank,  JellyfishArt.  JellyfishArt also tank raises their own Moon Jellyfish for Sale to the general public so that you can actually purchase pet moon jellyfish to stock your jellyfish aquarium with.

Jellyfish Fact: Is it Difficult to Keep Jellyfish Alive in Captivity?

Until just a few short decades ago scientist did not possess the technological expertise to keep jellyfish alive in captivity. Jellyfish are 95% water. They would be  liquefied instantly if sucked into a conventional water filtration system. Jellyfish can not be housed in a traditional square aquarium. They will get stuck in the corners and lack the higher brain functioning ability to get out. If there is not a flow of turbulence in the water, they are reduced to the equivalent of a bowl of jello. Keeping a jellyfish in a home aquarium was unthinkable. There was not a single jellyfish exhibit in a public aquarium anywhere in the world.

blue bladder jellyfish
Jellyfish were first displayed in a public aquarium just over twenty years ago in Monterey California. This feat was made possible by the pioneering work of German oceanographer, Dr. Wolf Greve.

Dr. Greve invented a circular aquarium that circulated water in a horizontal circular pattern. He dubbed his invention the Kreisel (German for carousel) tank. This revolutionary aquarium was originally designed for the study of arctic plankton. The tank’s circular design and water flow gently pushed the plankton away from the aquarium’s outer perimeter and toward the center of the tank. This technological breakthrough was essential in keeping jellyfish alive in a manmade environment.

Facts About Jellyfish: Do Jellyfish Really Glow in the Dark?

Go to any large public aquarium and you will watch exotic varieties of jellyfish fading almost hypnotically from one color to another. While it is nothing short of mesmerizing to observe a jellyfish exhibit, you are watching an orchestrated light show. Since most jellyfish are transparent or translucent in appearance, this beautiful display of coloration is nothing more than light passing through the jellyfish’s membranes. They are not actually glowing. So the question remains do jelly fish really glow in the dark? And the answer is yes; well sort of.

moon jellyfish, pet moon jellies. W

True jellyfish belong to the class Scyphozoa a subdivision of the phylum Cnidaria. No true jellyfish actually glows in the dark. There are two species of jellyfish like organisms within the phylum Cnidaria that are bioluminescent depending on how strict a definition is applied to the term bioluminescent. Although they are not really jellyfish they are commonly referred to as comb jellyfish and crystal jellyfish. Bioluminescence is the scientific term used to describe the chemical process through which an organism actually produces and emits light. Fire flies are bioluminescent.

comb jellyfish, W
Watch Invaders from Another Planet Video

Comb jellyfish do not require a fancy light show to produce their very own disco display. They are not, however, bioluminescent. They simply appear to be. Comb jellies are from an entirely different class (Ctenophora) than jellyfish. One of the defining parameters of what constitutes a jellyfish is the way in which it achieves locomotion. True jellyfish do this by expanding and contracting their hydroskeletons to create a kind of primitive jet propulsion. Mobility in comb jellyfish is achieved by the rabid pulsing of thousands of tiny oars distributed over 8 rows of legs extending from their main body. These legs are called combs, hence the name comb jellyfish. 

These creatures propel themselves through the water by beating their combs against the water in sequence. The combs are highly refractive. Even in lower light settings comb jellyfish give the appearance of producing their own disco light show. Scientists speculate that this hypnotic light display acts to entice the natural curiosity of potential prey.

Facts About Jellyfish: What Jellyfish Does Glow in the Dark?

Crystal jellyfish come closer to glowing in the dark than any other jellyfish. Although crystal jellyfish (Aequorea victoria) are not actually jellyfish either. Aequorea victoria are from the class Hydrozoa a subdivision of the phylum Cnidaria which includes their close relatives, the true jellyfish. Nor do crystal jellyfish actually bioluminescence. They fluoresce. The illusion of biochemical light emission is produced by a combination of two molecules; aequorin and green fluorescent protein (GFP). GFP produces brilliant neon green fluorescence when exposed to light in the blue or purple spectrums. GFP has been isolated by scientist and is being used in cellular research.  
crystal jellyfish, W
GFP was the protein Dr. Zhiyuan Gong and his colleagues at the National University of Singapore incorporated into the genome of zebra danio eggs to create the immensely popular freshwater aquarium fish, the Glofish. Further experimentation has progressed to the incorporation of this gene into mammals and most recently primates. It should be noted that none of these genetically engineered animals actually glow in the dark. They will, however, fluoresce under a backlight.

Facts About Jellyfish: What About Jellyfish Stings?

marine stinger warning sign

All Jellyfish have specialized organelles called nematocysts. These cells are full of venom and are present on the tips of a jellyfish’s tentacles. The stinging cells are triggered by touch. When triggered, the pressure in the nematocysts builds up to 2000 lbs. per square inch causing a microscopic lance to be ejected administering the jelly venom. A typical jellyfish contains millions of these stinging cells. Jellyfish do not actually attack humans. Their sting is nothing more than an autonomic response. This response serves the dual purpose being a self-defensive mechanism as well as paralyzing a jellyfish’s prey.  

Facts About Jellyfish: Are Jellyfish Stings Deadly?

That depends on which jellyfish you are stung by. Depending on the species in question, jellyfish stings range in severity from imperceptible to human beings to certain death without immediate treatment. Most jellyfish stings are more akin to a bee sting than anything life threatening. It should be noted that each individual reacts differently on a metabolic level to invasive toxins. Bee stings are little more than a minor annoyance to most people but there are those who must seek medical attention due to potentially life threatening allergic reactions to bee venom.

Watch the Worldwide Jellyfish Invasion!

Facts About Jellyfish: What is the World’s Deadliest Jellyfish?

box jellyfish stinger warning sign, W

The Sea Wasp holds the World Heavy Weight Championship title in that arena.  The sea wasp is one of twenty species of jellyfish collectively referred to as box jellyfish because they have a box-like rather than an umbrella shaped bell. Sea wasps invade the northern shores of Australia annually. This incursion into shallow waters begins at the onset of the rainy season around November and typically runs through to the end of May.  Some beaches have nets put in place prior to this annual invasion in an attempt to isolate beach goers from these deadly creatures. Other beaches are closed entirely.

Wasp jellyfish are one of the deadliest creatures on Earth. An adult sea wasp carries enough venom to kill 60 full grown adults. Death can occur in as little as 2-3 minutes depending on the number and severity of stings. This is quicker than any insect, spider or snake known to man. Approximately 1,000 people are stung by sea wasps annually resulting in 100 deaths.  

There have been over 5,500 casualties since the Australian government started keeping records of sea wasp fatalities in 1954.

Sting victims swimming in deeper waters frequently die from drowning or cardiac arrest before they are able to make it back to shore or their boat. All life guards on Australia's northern beaches are equipped with box jellyfish anti-venom kits. Survivors of box jellyfish attacks describe the pain as excruciating. Secondary mortality symptoms include; respiratory paralysis, neuromuscular paralysis, and cardiovascular collapse.

While box jellyfish may hold the title for being the deadliest creature in the world, pound for pound Irukandji jellyfish are even deadlier. For generations, the Irukandji aborigines spoke of a mysterious presence in Australian waters that brings unspeakable pain. Irukandji syndrome was first documented by Hugo Flecker in 1952. There are at least six species of jellyfish capable of producing Irukandji syndrome. The first of these jellyfish, Carukia barnesi, was discovered in 1964 by Dr. Jack Barnes. This jellyfish was smaller than his finger nail. 

tiny Irukandji jellyfish, W

Yet Dr.Barnes was so convinced that he had just found the creature responsible for the mysterious deaths off the coasts of Autraila that 
he intentionally stung himself, his son and the lifeguard on duty. All three had to be hospitalized for Irukandji syndrome. Irukandji jellyfish venom is 100 times more potent than cobra venom and 1,000 times more powerful than that of a tarantula.  An anti-venom has yet to be developed for Irukandji syndrome. Doctors are helpless to prevent the toxin from spreading in sting victims. They can only threat the symptoms of the venom and hope the patient lives through the agonizing experience.

Neither box jellies or Irukanji jellyfish are actual jellyfish. They are members of the class Cobozoa one of the four classes contained within the phylum Cnidaria which also contains Scyphozoa or what is known as "true jellyfish."

Facts About Jellyfish: How do you Treat Jellyfish Stings?

sting, PB

Contrary to popular belief, urinating on a jellyfish sting is not the best emergency medical treatment. In fact, you may only succeed in making the problem worse.

Jellyfish stingers remain embedded in the skin, just like a bee’s stinger. The first step is to deactivate the stingers to prevent additional venom from entering the victim’s system. Dosing the area with vinegar is the best way to neutralize jellyfish venom and prevent nematocysts from being triggered.

If vinegar is unavailable, anything with a high acid content can be used instead. Rinse the stings thoroughly with sea water if no acidic compounds are available. DO NOT use freshwater.  Freshwater will activate any unfired nematocysts and result in the further release of venom.

Remove the jellyfish stingers. This can be accomplished by rubbing the skin vigorously with sand or scraping the skin with a dull, flat object. NEVER ALLOW your bare hands to come in contact with the stingers.  Use a towel or gloves.

Seek immediate medical treatment. Lifeguards are equipped with emergency first aid kits and the proper training to treat indigenous jellyfish stings. If immediate medical assistance is not available watch the victim for: shortness of breath, wheezing, tightening of the throat, flushed skin, weakness, nausea, or dizziness until help arrives. These may be signs of the onset of anaphylactic shock, which is potentially life threatening.

Learn the Proper Way to Treat a Jellyfish Sting

Watch Dr. Mike Leahy Sting Himself with a Box Jellyfish on Purpose!

Facts About Jellyfish: What is the World’s Largest Jellyfish?

The largest known jellyfish species is the Arctic lion’s main jellyfish followed closely by Nomura’s jellyfish off the coasts of China and Japan. The largest lion’s mane ever officially documented washed up on the shoreline of Massachusetts Bay in 1870. Its bell measured 7.5 feet (2.28 meters) in diameter and its tentacles stretched to a length of 120 feet (36.5 meters). There have been claims of larger jellyfish being discovered since then but none have been officially documented. This photo has been circulating the internet lately. It is a fake, probably somebody’s idea of fun playing with their Adobe Photoshop. This pictures a Nomura's Jellfish at 5 times its actual size.

lion's main jellyfish, PB
There is a widely held misconception that the Portuguese man o’ war is the largest known jellyfish. The Portuguese man o’ war is also not an actual jellyfish. It is a massive colony of 1,000,000s of Hydrozoa functioning in unison as a single organism. Hydrozoa are the fourth class of the phylum Cnidaria.

About Jellyfish: Jellyfish Facts

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