Jellyfish are otherworldly, gently propelling their umbrella-shaped bodies through the ocean. They can also be dangerous, as some jellyfish are amongst the most venomous animals on the planet.
Jellyfish come in all sizes, ranging from coastal species that are smaller than a grape to deep sea creatures that can be larger than blue whales! With all of this biodiversity, there’s a lot to learn about jellyfish. We’ve rounded up the web’s most extensive resource on jellyfish, including interesting species and must-know facts.
The 15 Must-Know Types of Jellyfish
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1. Lion’s Mane Jellyfish (Cyanea capillata)
The lion’s mane jellyfish is the largest species of jellyfish, with some specimens coming close to the size of a blue whale. The biggest recorded lion’s mane jellyfish had a seven-foot (2.13 m) diameter bell and 112 feet (34.13 m) long tentacles. Their name comes from the approximately 1,200 tentacles that make up their mane.
Lion’s mane jellyfish are mostly found floating in the open ocean in the Arctic and North Pacific Oceans. Lion’s mane jellyfish are bioluminescent and have tentacles covered in millions of stinging cells, holding venom that can be very painful to humans. But since they’re mostly found in cold water, lion’s mane jellyfish don’t normally interact with humans.
2. Upside-Down Jellyfish (Cassiopea sp.)
Upside-down jellyfish act differently than most jellyfish. Instead of floating bell-up through the ocean, they sit with their bell on the ground, extending their tentacles up to catch food. Upside-down jellyfish are usually found in sheltered coastal areas of tropical waters around the world.
Upside-down jellyfish have a unique defense and hunting mechanism. These jellyfish release mucus filled with nematocysts into the water to capture prey and ward off predators. While the venom from a single upside-down jellyfish isn’t very strong, once one jellyfish releases envenomated mucus the rest of the colony follows suit, making the water dangerous for small fish.
People snorkeling through these waters have reported a slight stinging sensation in the water, likely caused by the upside-down jellyfish’s mucus.
3. Moon Jellyfish (Aurelia aurita)
Moon jellyfish are one of the most common jellyfish and can be found in coastal waters of all oceans except the Arctic Ocean. They have distinctive half circles on the bell which are reproductive tissues. Their sting is not strong enough to penetrate human skin so they’re safe to touch, making moon jellyfish common aquarium species.
Moon jellyfish are bioluminescent and glow a light purple when bumped in the dark. Moon jellyfish are one of the species most commonly eaten by people.
4. Nomura Jellyfish (Nemopilema nomurai)
One of the largest species of jellyfish, the Nomura jellyfish can grow up to six feet (1.82 m) in diameter and usually weigh over 400 pounds (181.43 kg). Nomura jellyfish are found in the seas between China and Japan and often create jellyfish blooms that decimate fish populations.
Nomura jellyfish have become such a big problem for China and Japan that special research teams have been formed to understand why this species grows so large and how the population can be reduced to a safer level.
These scientists believe Nomura jellyfish are able to grow so large from a combination of hydroelectric projects and farming along the Yangtze river that have created enriched nutrient habitats in the Sea of Japan.
While it should be easy to remove jellyfish blooms from the water, Nomura jellyfish have a special defense mechanism. When they feel threatened they release billions of sperm and eggs which attach to the ocean floor and grow into more jellyfish.
Little is known about the deep red jellyfish because their habitat is hard to reach. Deep red jellyfish are found deep in the water of the Arctic Sea, 3,000 feet (914.4 m) or more below the surface. These jellyfish are much smaller than many other species, reaching a diameter of only two centimeters (0.78 inches).
Deep red jellyfish don’t go through a polyp phase and it’s unknown whether they reproduce sexually or asexually. Because of all of these unique characteristics, the deep red jellyfish has been described as alien-like by scientists.
The four-handed box jellyfish is found in the West Atlantic Ocean, Gulf of Mexico, and the Pacific Ocean. This jellyfish is transparent and has a bell about the size of a fist with tentacles up to 13 feet long (3.96 m).
The four-handed box jellyfish is known for its venomous sting which can be lethal to small children and has been known to kill people within minutes of being stung.
The sea wasp jellyfish is found in the coastal waters of Australia and Southeast Asia. This is the largest cubozoan jellyfish with a bell of approximately eight inches (20.32 cm) and tentacles up to ten feet long (3.04 m).
The sea wasp is the most venomous jellyfish and produces the strongest and fastest reaction of any venomous animal. Contact with the ten-foot (3.04 m) tentacles causes immediate pain followed by cardiac failure, leading to death of the prey within a few minutes time. This venom is best suited for capturing prey and isn’t useful to deter predators, so sea wasps are a common food source for leatherback turtles and other large sea creatures.
Scientists are researching why the sea wasp jellyfish’s venom is so powerful, and have found a special component of the venom that drills holes in the victim’s red blood cells. Through clinical trials researchers are getting closer to producing an antidote to the sea wasp jellyfish’s venom.
8. Immortal Jellyfish (Turritopsis dohrnii)
The immortal jellyfish is smaller than a pinky nail with a red stomach visible in the middle of its transparent bell. This jellyfish is found in temperate to tropical waters around the world.
As the common name suggests, this species of jellyfish is thought to be immortal due to their unique life cycle. Instead of completing the life cycle and dying after the medusae phase, the Turritopsis dohrnii settles on the seafloor and becomes polyps again, which spawn new clones of the original jellyfish.
This life cycle quirk isn’t just seen at the natural end of their life, but is also used as a defense mechanism. When threatened by predators or starvation, this jellyfish transforms back into a polyp and starts over again. This cellular process is called transdifferentiation and is being researched by scientists for its potential applications in the medical field.
The mangrove box jellyfish is found on the seafloor in coastal mangrove forests in Central America. They are relatively small in size, with a bell the size of a grape and tentacles about an inch long.
While they are closely related to the sea wasp and other highly venomous box jellyfish, their venom is not harmful to people. Mangrove box jellyfish are facing habitat loss because mangrove forests are among the most threatened ecosystems in the world.
These mangrove forests are cleared for development, agriculture, and fish farming, leaving the mangrove box jellyfish with no suitable habitat.
Crystal jellyfish are found in the Pacific Ocean from the Bering Sea to Southern California. These nearly transparent jellyfish grow up to ten inches (25.4 cm) in diameter with long, wispy tentacles.
While crystal jellyfish appear clear, they use bioluminescence and glow green-blue when bumped. The bioluminescent cells from crystal jellyfish have been used as genetic markers by scientists studying genes.
Crystal jellyfish can eat prey up to half their body size by using their specialized mouth. They are common prey species for larger creatures like ocean sunfish, which can be problematic. Plastic bags and other trash floating in the water look just like crystal jellyfish, causing problems for the species that eat them.
The black sea nettle is one of the giant jellyfish species, with bells reaching over three feet (0.91 m) in diameter and tentacles reaching twenty-five feet (7.62 m) in length. Little is known about the black sea nettle because they’re deep-sea dwellers and are difficult to raise in captivity.
They have been known to form dangerous blooms in San Diego Bay and are usually found off the southern coast of California and down the Pacific Coast of Mexico.
Black sea nettles have been observed to provide both food and protection for Pacific butterfish: the butterfish eat the plankton gathered by the black sea nettle and hide inside the jellyfish’s bell when danger is near.
The fried egg jellyfish gets its name from the distinctive yellow circle on the center of their bell. They are also called Mediterranean jellyfish and only live for six months, from summer to winter, and die when the water gets colder.
They are primarily found in the Mediterranean, Adriatic, and Aegean Seas and grow to approximately sixteen inches (40.64 cm) in diameter. They have a mild sting that usually doesn’t have an effect on people, and have been known to transport small animals like crabs on top of and inside their bell.
Atolla jellyfish are found in the deepest parts of the ocean all over the world. Living between 3,280-13,000 feet (999.74 – 3,962.4 m) below the surface, atolla jellyfish live in the midnight zone of the ocean and use bioluminescence to deter predators instead of to attract prey.
With a bell diameter of about six inches (15.24 cm), the atolla jellyfish’s natural red coloring acts as camouflage in the deep sea. When threatened they use bioluminescence to flash a bright blue to startle predators.
Cauliflower jellyfish or crown jellyfish are found in subtropical oceans throughout the world and have a bell approximately seven inches (17.78 cm) in diameter. While they are one of the most venomous jellyfish, their venom is not harmful to humans.
These jellyfish move up and down throughout the ocean, spending the daytime deep in the water and coming closer to the surface at night. They are also bioluminescent and glow when threatened by predators. Cauliflower jellyfish are commonly eaten by people in Japan and China and have even been used for medical purposes
White-spotted jellyfish are found in tropical waters of the western Pacific Ocean. They’re named for the distinctive white spots on their bell and tentacles. While they do have venom, white-spotted jellyfish aren’t harmful to humans and don’t use venom to capture their food. Instead, these jellyfish are filter feeders and eat mostly microscopic zooplankton.
White-spotted jellyfish often form blooms that disrupt local ecosystems by removing all of the plankton in the water. These jellyfish become invasive species in areas with no marine snails, the most common predator of white-spotted jellyfish.
All jellyfish are invertebrates, so they have no bones or even cartilage to support their body. Most jellyfish have umbrella-shaped bells that can be contracted to propel themselves through the water. Their tentacles can be covered in stinging cells called nematocysts. These cells are used to capture prey and defend against predators.
Most jellyfish live less than a year, and some species of smaller size live only a few days.
Jellyfish are members of the phylum Cnidaria, which also includes corals and anemones. All animals in the phylum Cnidaria have specialized stinging cells that are used to protect from predators and capture prey.
Generally, the term jellyfish refers to a single phase in a cniderian’s life cycle: the medusa phase, which is also the reproductive phase. A cniderian’s life cycle starts with fertilized eggs that become larvae called planula. These planulas attach to the ocean floor and grow into polyps.
Each polyp can bud off several miniature medusas, which grow into reproductive adult medusas. Only these adult medusas are actually jellyfish, so baby jellyfish aren’t jellyfish at all!
Jellyfish are also members of the subphylum Medusozoa. This is the point where jellyfish branch off from other Cnidaria, and are further categorized into four classes.
There are four classes of jellyfish: scyphozoa, cubozoa, hydrozoa, and staurozoa.
There are over 200 species of scyphozoa or ‘true jellyfish’, which live in all the world’s oceans. Some are deep-sea jellyfish, but most scyphozoa live near coastal waters. Scyphozoa are known as true jellyfish because they have both a polyp phase and a medusa phase.
The class cubozoa includes only box jellyfish, which is about 20 species. Cubozoa are different from other jellyfish because their bell is cube-shaped instead of round. Box jellyfish are primarily found in tropical and subtropical waters, and some species can produce very strong venom.
The class hydrozoa includes more than just jellyfish. Hydrozoa is one of the more diverse classes of cnidarians. Not all hydrozoa species include the medusa phase, so not all hydrozoans are jellyfish.
There are about 1000-1500 species of hydrozoa that form medusa and therefore are jellyfish, and many more species that stay in the polyp stage and can’t be considered jellyfish. Hydrozoans can be found in all oceans and are most diverse in warm, shallow waters.
The class staurozoa is different from the other three classes of jellyfish. Staurozoa are also known as stalked jellyfish, and spend their whole lives attached to rocks or algae rather than swimming freely during the medusa phase. There are about 50 species of staurozoa and these jellyfish are exclusively found close to the shoreline in cold water.
Jellyfish Habitat and Range
Jellyfish can be found in saltwater and brackish or slightly salty water. Most jellyfish are found in coastal zones but some species live in deep-sea or near the surface in the pelagic zone of the open ocean. Jellyfish can be found in every ocean on Earth.
Jellyfish are found all over the world and in all parts of the ocean. Smaller, translucent jellyfish are commonly found in coastal zones. Many deep-sea species are red, which actually allows them to blend into the water.
Both coastal and deep-sea species of jellyfish can be bioluminescent, allowing them to produce their own light to attract prey or deter predators.
All jellyfish are carnivores. Most jellyfish eat small plants, copepods, fish eggs, small fish larvae, and the larvae of other marine animals. Larger jellyfish will eat lobsters, shrimps, barnacles, crabs, and whatever else they can tangle up in their tentacles. Some jellyfish even eat other jellyfish!
Jellyfish catch food by trapping it in their tentacles. The poison in the tentacles will paralyze the food, which are then grabbed by the jellyfish’s oral arms and moved into their mouth. Small jellyfish don’t actively pursue prey, but will eat whatever is available in the water around them. Larger jellyfish may actively capture and kill their food and some have a poisonous sting that can be shot out to capture potential prey.
Jellyfish have several predators which are mostly larger carnivorous sea creatures. Spadefish, sunfish, and sea turtles species often eat jellyfish. Larger jellyfish will eat smaller jellyfish. Some birds will commonly eat coastal jellyfish. People can be jellyfish predators too, and jellyfish is considered a delicacy in some cultures!
As ocean temperatures rise, some jellyfish populations are increasing because their predator populations are decreasing. This is leading to jellyfish blooms becoming more common and disrupting fisheries and powerplants that use seawater for cooling. Jellyfish blooms are also dangerous to people swimming in inhabited waters.
While all jellyfish sting, not all jellyfish have venom strong enough to impact humans. Many species of jellyfish pose no threat to people, and swimming with jellyfish is a common tourist activity in some parts of the world.
Jellyfish capture prey and protect themselves by using the stinging cells on their tentacles. These cells are called nematocysts, which release a stinging barb coated in venom to cause a chemical reaction with their prey.
Jellyfish species have various toxins inside their nematocysts that incapacitate their prey in different ways. More than 150 million jellyfish stings happen in the world each year.
If you’re stung by a jellyfish, the symptoms will be different depending on the type of jellyfish. Mild stings usually cause minor pain and itching, sometimes with a lasting rash. More serious stings can lead to difficulty breathing, muscle cramps, chest pain, numbness, skin blistering, nausea, and even difficulty swallowing.
To treat mild stings, rinsing the stung area with seawater is an important first step to remove any nematocysts that are still on the skin. You should also use tweezers to remove any tentacles that are still on the skin. Apply an ice pack to reduce swelling.
For some species, applying freshwater or vinegar causes more nematocysts to be released and makes the stinging sensation worse. Vinegar can be applied to reduce the stinging sensation, but should only be done after the area is fully cleaned and all nematocysts have been removed.
Some jellyfish sting ointments and treatments, but generally you just need to remove any tentacles and nematocysts and leave the sting alone to heal without becoming more inflamed.
1. Urine will relieve jellyfish sting.
Perhaps the most common jellyfish myth tells us that urine will relieve a jellyfish sting. The idea is that urine is acidic enough to counteract the nematocysts and would relieve the stinging sensation. This isn’t true, unless the urine came from a severely dehydrated person.
Your best bet to relieve pain from jellyfish stings is to thoroughly clean the stung area with seawater. Vinegar can be used to relieve the sting, but cleaning the area is most common.
2. Jellyfish attack humans.
Another jellyfish myth is the idea that jellyfish attack humans. This is also false, as jellyfish have little ability to choose what direction they float. Jellyfish also wouldn’t be attempting to eat a person if they were in the same area, so you’re safe from jellyfish attacks. While you might be stung if you’re in the same water as a jellyfish, it wasn’t an intentional attack!