Jellyfish are fascinating sea creatures and come in a vast range of sizes and appearances. This article will show you some of the most intriguing types of jellyfish with a selection of the most common, dangerous, prettiest, weirdest, tiniest, and even some that glow in the dark.
How Many Species of Jellyfish Are There?
Before we dive in, let’s take a quick overview of these fantastic animals starting with considering how many species of jellyfish there are.
There are about 1,800 species inside the classes of medusozoan Cnidaria that marine scientists regard as jellyfish.
Jellyfish are the common names given to an extensive range of animals in the subphylum Medusozoa, part of the phylum Cnidaria, which includes four major classes.
Sometimes you’ll see this question answered with only the class Scyphozoa, which are occasionally called true jellies. However, this is only part of the picture.
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In addition to Scyphozoa (true jellyfish – about 200 species), there are also Cubozoa (box jellyfish – about 50 species), Staurozoa (stalked jellyfish – about 50 species), and Hydrozoa medusae (tiny, predatory animals – about 1,500 species).
You can find jellyfish everywhere in the world’s oceans, from the surface of tropical waters to the deepest depths, including in the Mariana Trench. While almost all jellyfish are found exclusively in saltwater, some hydrozoans live in freshwater.
Hydrozoans are so small that you’re unlikely to come across them, so we will concentrate on the types of jellyfish you’re more likely to see.
3 Most Common Jellyfish Species You Can Find
The most common jellyfish will depend on where in the world you are. These three are some of the most common in popular global holiday destinations.
Moon Jellyfish (Aurelia aurita)
Moon jellyfish are a very common scyphozoan jellyfish species about 25–40 cm (10–16 in) in diameter, which is seen at or near the surface in coastal waters. You can find moon jellies in almost any ocean, except the Arctic, as they will tolerate a wide range of temperatures between 6 – 31°C (43 – 88°F).
Moon jellyfish often have a distinctive purple color. This can, on occasion, even be seen at night as they possess bioluminescence which seems to activate once they are touched, perhaps as a warning mechanism.
You can identify a moon jelly by the ring of small circles which appear around the center of their round translucent bodies above their reproductive organs.
Moon jellyfish are filter feeders and will drift along the surface to be found in large numbers wherever there are plankton blooms. Nematocyst-covered stinging tentacles on the animal’s underside trap plankton and pass it along to the jellyfish’s mouth where it’s digested.
Although moon jellyfish possess venom to trap their food, they are not considered harmful to humans. Indeed, swimmers and snorkelers may come into contact with them and not feel any stinging sensation at all.
Moon jellyfish are not especially strong swimmers, so they are readily carried by currents and tides. You’ll often see them washed onto beaches, particularly in rough weather.
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Upside-Down Jellyfish (Cassiopeidae)
Upside-down jellyfish are commonly seen in sheltered tropical waters and enjoy mangrove swamps, seagrass beds, and mudflats.
Unlike most jellyfish, which swim with their tentacles facing downwards, the upside-down jellyfish can always be found, unsurprisingly, upside-down. Snorkelers usually see these jellyfish resting on the bottom with their tentacles facing upward.
Upside-down jellyfish release stinging cells into the water around them, which both stun prey and act as a mechanism to keep predators away.
In areas where there are many upside-down jellyfish, swimmers often feel a slight stinging sensation in the water.
Although these jellyfish can catch and digest small food items, they get most of their energy from sunlight. A symbiotic species of photosynthetic dinoflagellate lives in their tentacles and provides the jellyfish with food.
The jellyfish rests upside-down, pointing its energy-producing tentacles toward the sun to maximize the amount of light received.
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White-Spotted Jellyfish (Phyllorhiza punctate)
Our third common jellyfish is one originally native to the western Pacific that has now spread around warm and temperate waters to become common as an invasive species.
The white-spotted jellyfish, also called the floating bell and Australian spotted jellyfish, filter feeds on zooplankton while it swims and can reach a pretty significant 50 centimeters / 20 inches in diameter.
In keeping with the rest of our common jellyfish, the venom from the white-spot is mild and isn’t considered harmful to people.
These jellyfish drift in significant numbers eating large quantities of zooplankton. Indeed, they’re so efficient that they can filter food from up to 50,000 liters (13,000 US gal) of seawater per day.
In areas such as the Hawaiian Islands, Gulf of California, Gulf of Mexico, and the Mediterranean Sea, where they are an invasive species, they can consume so much plankton that native species cannot get enough food. This can affect the populations of local fish, shrimp, crab, and other animals.
It is believed that the jellyfish have traveled around the world in ships’ ballast tanks. Juvenile animals are sucked into the tanks and later dumped into new waters. The jellyfish can thrive where their regular predators, marine snails, are absent.
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3 Types of Dangerous and Deadly Jellyfish
There are jellyfish stings that can be very painful or even deadly. It’s always best to be wary and stay clear unless you know that the jellyfish you’ve seen is safe. Here are three of the most dangerous and deadly stinging jellyfish of all.
Four-Handed Box Jellyfish (Chiropsalmus quadrumanus)
There are over 50 species of box jellyfish, and thankfully not all of them are deadly. Many give no more than a painful sting to healthy people.
However, of the ones that can cause you harm, the four-handed box jellyfish has caused its fair share of deaths.
The four-handed box jellyfish lives in the western Atlantic Ocean, Pacific Ocean, and the Gulf of Mexico. They are usually found in warm, open waters. However, they are sometimes pushed close to the coast by weather conditions and can wash up on shore when there are high winds.
The jellyfish is colorless, transparent, and measures approximately 14 centimeters / 5.5 inches across its cube-shaped body. Seven to nine stinging tentacles up to 4 meters / 13 feet long hang down in the water to catch food.
Each tentacle is covered with stinging cells, and while they usually catch prey that includes small fish, contact with them can be hazardous, particularly to children.
The jellyfish sting can cause intense pain, shock, and respiratory and cardiac function impairment. Antivenom needs to be given quickly to relieve the symptoms and prevent severe injury or death.
Sea Wasp Jellyfish (Chironex fleckeri)
The sea wasp, also known as the Australian box jellyfish, is highly venomous and lives in waters around the coast of South East Asia and northern Australia.
The sea wasp is the largest box jellyfish known, and the main body can reach approximately 25 centimeters / 10 inches. Fifteen tentacles trail below the body, and these extend to about three meters / 10 feet when the animal is hunting its regular diet of shrimp and small fish. When swimming, the tentacles contract up into the body to become about 150 millimeters / 6 inches long.
Unfortunately for swimmers, this jellyfish is almost entirely transparent and very difficult to see. Stinging cells on the tentacles are activated by pressure and release an extremely potent venom that instantly causes excruciating pain, leading to unconsciousness and death if untreated.
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Nomura Jellyfish (Nemopilema nomurai)
The Nomura, found in the seas between China and Japan, is one of the largest jellyfish species and can reach up to 1.8 meters / 6 feet in diameter with an astonishing weight of over 180 kilograms / 400 pounds.
Nomura jellyfish can deliver a nasty venom that is difficult to treat because it is made of a particularly complex mix of protein toxins. Symptoms from a sting include swelling, itching, severe pain, inflammation, and in extreme cases, death.
However, it’s not only the dangerous venom that can make this jellyfish deadly. Blooms of the species can wipe out fish populations, particularly in areas where natural predators such as tuna, swordfish, and leatherback turtles are missing.
3 Types of Pretty Jellyfish
Jellyfish are not only deadly. Different kinds of jellyfish can be beautiful too. Here are three of the prettiest to look at.
Bloodybelly Comb Jellyfish (Lampocteis cruentiventer)
This jellyfish is a beautiful comb jelly with a striking red coloration with a special purpose.
The bloodybelly preys on deep-sea bioluminescent animals that, once swallowed, would usually make the animal glow and be vulnerable to its own predators. Deep underwater red appears as black, and so by making its stomach a deep red color, the bloody belly manages to block the bioluminescence and keep itself hidden.
Bloodybelly comb jellies don’t have tentacles. Instead, it moves by beating eight rows of cilia hairs that run along its body. As it swims, the cilia themselves give off an impressive light show which it may use selectively to attract food.
Cauliflower Jellyfish (Cephea cephea)
The cauliflower jellyfish has lumpy projections on the top of its bell, which are said to resemble the vegetable from which it takes its name. Now, this might not sound particularly pretty, but with its stunning purple-blue coloration and yellow-orange tentacles, this is one beautiful jellyfish.
The cauliflower jellyfish, also known as the crown jellyfish, is found in tropical waters of the western Indo-Pacific, eastern Atlantic, and the Red Sea.
The crown jellyfish feeds on plankton and shrimp and can grow to up to 60 centimeters / 24 inches in diameter. They tend to spend their days in deep water before moving close to the surface to feed at night.
This jellyfish possesses one of the most potent venoms of any species. However, luckily a sting is considered harmless to humans in reality.
Cauliflower jellyfish are considered a delicacy in China and Japan and are also used in traditional medicine.
Flower Hat Jellyfish (Olindias formosus)
Our last pretty selection is a curious hydromedusa found in a limited range in the northwestern Pacific off central and southern Japan, South Korea, and waters around Brazil and Argentina.
The flower hat rests on the sea bed during the day hiding amongst rocks or in seagrass. At night it floats up into the water to hunt for a meal of small fish.
Thanks to the gorgeous colors and shape, the jellyfish makes our most beautiful list. Indeed it would be easy to see one on the bottoms and think it was a brightly patterned hat that had fallen into the water.
However, it certainly wouldn’t be a good idea to pick this hat up as the jellyfish can deliver a painful sting resulting in a nasty and long-lasting rash in most cases.
3 Types of Weird Jellyfish
You could say that most jellyfish are pretty strange. However, some stand out, and here are some especially weird jellyfish.
Black Sea Nettle Jellyfish (Chrysaora achlyos)
Our first weird jellyfish is one of the largest deep-sea jellyfish species in the ocean. You can find the black sea nettle jellyfish in the Pacific Ocean off California and Mexico, and it is known to grow to a diameter of about one meter / three feet in diameter with arms longer than five meters / 16 feet.
Scientists know little about this jellyfish, and it was only discovered in 1989. The bell on mature animals has an almost black opaque coloration unique amongst jellyfish found in the area.
Large blooms of black sea nettles have been spotted at the surface in waters off Southern California and Baja California in 1989, 1999, and 2010. However, it is a mystery why the animals congregate together in such large numbers in shallow water.
Fried Egg Jellyfish (Cotylorhiza tuberculata)
What could be weirder than a jellyfish that resembles a fried egg? Well, our second choice is precisely that. When viewed from above, this jellyfish looks pretty much like a fried egg floating about.
The fried egg jellyfish is found in the Mediterranean Sea, Adriatic Sea, and Aegean Sea. It reaches a relatively large 40 centimeters / 16 inches in diameter and is usually seen drifting while feeding on phytoplankton and zooplankton.
Fortunately, if you happen to come into contact with this jellyfish, the most that you’ll typically suffer is a mildly itchy rash. Indeed the jellyfish sting is so weak that small fish are often seen sheltering amongst the tentacles of the fried egg jellyfish as protection from other, more aggressive animals.
Large annual blooms of these jellyfish can interfere with commercial fishing and tourism due to their sheer numbers in the water. Fishing boats will try and actively remove large numbers of the jellyfish at the start of each season to try and limit their impact during the summer months. Fortunately, the fried egg jellyfish only has a lifespan of about six months, giving a respite during the winter.
Narcomedusae Jellyfish (Narcomedusae order)
The narcomedusae is a fascinating order of hydrozoans said by some to have a Darth Vader-like visual appearance.
However, if their curious appearance wasn’t enough, the narcomedusae have a unique arrangement of two stomach pouches that allow them to eat weirdly. As they swim, the jellyfish holds its tentacles out in front to ambush its prey. Any captured food is fed into whichever stomach happens to be empty at the time.
Unlike most jellyfish, which lay eggs, narcomedusae grow inside their mother. When they’re large enough to leave and swim in the open ocean, they can attach to other jellyfish to be carried along and even receive nutrition by feeding on the host’s flesh.
Narcomedusae jellyfish are usually found in the open sea in deeper waters, particularly in the Mediterranean.
3 Types of Small Jellyfish
Not all jellyfish are huge. Many types of small jellyfish are equally fascinating. The smallest are the tiny Staurocladia and Eleutheria creeping jellyfish that can be less than half a millimeter in diameter. We’re going to look at three, which are a little larger, so you can see them with the naked eye. However, they are still definitely small.
Deep Red Jellyfish (Crossota norvegica)
The deep red jellyfish is a beautiful hydrozoan that reaches just two centimeters / 0.7 inches in size.
It’s unlikely that you’ll come across this particular tiny jellyfish on holiday as it’s found deep in the Arctic Ocean below 1,000 meters / 3,300 feet.
The deep red jellyfish hunts with stinging nematocyst cells that produce acid to stun its zooplankton prey.
Due to its deepwater habitat, not much is known by scientists about the behavior and reproduction of the deep red jellyfish. However, it is undoubtedly a stunning jellyfish despite its small stature.
Immortal Jellyfish (Turritopsis dohrnii)
The immortal jellyfish is a tiny animal found in temperate and tropical waters with an astonishing ability to live on after its normal life cycle.
The transparent bell of the immortal jellyfish measures just 4.5 millimeters / 0.15 inches in diameter. Juveniles only have eight tentacles, whereas adults have 80–90.
The incredible attribute of this tiny jellyfish is its ability to live on after its normal life cycle is complete. Instead of dying after its adult phase is finished (or when facing a lack of food or threat from predators), the animal drops to the seabed and becomes a polyp once more and spawns new clones to live again.
The irukandji jellyfish are tiny, but they could equally fit into the dangerous category.
These tiny transparent species of box jellyfish with 16 known species grow from 5 millimeters / 0.2 inches to 25 millimeters / 0.98 inches wide. They have four long tentacles, ranging from only a few centimeters to 1 meter / 3.3 feet in length.
Irukandji jellyfish are found in the coastal waters of northern Australia and are considered to be one of the most venomous jellyfish in existence. They have stingers on both their tentacles and, unusually, their bell and can fire them into swimmers causing painful stings known as Irukandji syndrome, which can be deadly.
It is said that between 50 and 100 people are hospitalized each year after being stung by an irukandji jellyfish. Fortunately, when properly treated by medical professionals, stings are not usually fatal.
3 Types of Glowing Jellyfish
Finally, let’s look at some beautiful luminous jellyfish that give off their own incredible light show.
Crystal Jellyfish (Aequorea victoria)
The crystal jellyfish is a hydrozoan jellyfish found off the west coast of North America. It is colorless and almost completely clear during the day. However, at night it puts on a spectacular glowing light show.
Crystal jellyfish produce flashes of alternating blue and green colored light at points along the outsides of their bells produced by releasing calcium-reacting photoproteins.
Scientists have isolated the crystal jellyfish proteins and are using them in medical research, pursuing cures for cancers and genetic diseases.
Atolla Jellyfish (Atolla wyvillei)
The Atolla jellyfish, also known as the coronate medusa and alarm jellyfish, is found in deep-sea environments worldwide at between 1,000 and 4,000 meters / 3,200 – 13,000 feet below the surface.
In common with many deepwater jellyfish, the atolla has a deep-red color. To go with this impressive coloration, the atolla can put on a stunning bioluminescent light show that it uses as an unusual defense mechanism.
Typically jellyfish and other animals use bioluminescence to lure their prey. However, the atolla jellyfish appears to use it to flee when threatened.
The atolla sets off spectacular flashes designed to lure in other predators when under attack. While this might sound crazy, the theory is that the new predator will attack whatever was trying to eat the atolla leaving the jellyfish to make its escape.
Lion’s Mane Jellyfish (Cyanea capillata)
The last of our types of jellyfish is the lion’s mane jellyfish which is known as being the largest in the world.
The largest-ever lion’s mane jellyfish had a bell with a diameter of 2.1 meters / 7 feet. Each fully grown jellyfish can have up to 1,200 tentacles, which can reach up to 36.6 meters / 120 feet long.
In addition to its impressive size, the lion’s mane jellyfish is bioluminescent so that it can glow in the dark underwater. It is thought that the jellyfish uses this light to attract and catch its favored food of small fish, crustaceans, and other jellyfish in its long tentacles.
What is the Deadliest Type of Jellyfish?
The deadliest of all types of jellyfish stings is from the sea wasp jellyfish (Chironex fleckeri).
Between 1884 and 2021, the sea wasp jellyfish sting is known to be directly responsible for at least 64 deaths. So deadly is the venom from this jellyfish that it is said that one animal carries a sufficient amount to kill 60 adults.
What is the Prettiest Jellyfish?
We think that the prettiest of all the types of jellyfish species is the flower Hat jellyfish (Olindias formosus).
While beauty is very much in the eye of the beholder, this jellyfish has stunning markings and coloration that make it stand out.
Can You Have Jellyfish as a Pet?
Yes, you can have a jellyfish as a pet. Among the suitable jellyfish types are the moon jellyfish (aurelia aurita).
You need a special type of aquarium that’s designed to circulate the water without risking sucking the delicate jellyfish into the filter.
Jellyfish aquariums are incredibly relaxing to watch. Many come with color-changing lamps to show off the jellyfish in ever-changing light as they circulate round and round.
While you’re not going to take a jellyfish for a walk or hug it, they certainly make a fascinating feature in your home.
So there you have it. Eighteen types of jellyfish that are common, dangerous, pretty, weird, tiny, glowing, or a combination of one or more.
Which is your favorite? Is there a jellyfish that you think we’ve missed out? Let us know in the comments what you think the prettiest jellyfish is.
British-born Dan has been a scuba instructor and guide in Egypt's Red Sea since 2010.
Dan loves inspiring safe, fun, and environmentally responsible diving and particularly enjoys the opportunity to dive with sharks or investigate local shipwrecks.
When not spending time underwater, Dan can usually be found biking and hiking in Sharm's desert surroundings.