Is your little one obsessed with jellyfish? We can relate. Jellyfish are among the most intimidating and intriguing creatures of the marine world, so it’s no surprise that kids and adults alike find them endlessly fascinating.
Take a few minutes to revel in these wonderfully weird facts about jellyfish. You might be surprised at what you don’t know about these beautiful creatures (especially number 8!)
Facts about jellyfish you need to know
So, with that in mind, let’s dive right into what makes jellyfish such amazing marine creatures.
Jellyfish are not fish
Despite their name, jellyfish are not actually fish! While it might sound confusing to call something a fish that isn’t, this is actually quite a common thing in the animal kingdom. Jellyfish are actually a type of invertebrate known as a cnidarian. They’re closely related to corals and sea anemones.
There are over 2,000 species of jellyfish
There are over 2,000 species of jellyfish and their close relatives that fill the world’s oceans. This vast variety allows jellyfish to live in every ocean in the world, even the chilly Antarctic Ocean. There are around 45 species of box jellyfish alone! In the waters around Bristol, species like the common moon jellyfish (Aurelia aurita), the larger barrel jellyfish (Rhizostoma pulmo), and the blue jellyfish (Cyanea lamarckii) all float, but be careful because they can give you a nasty sting.
Some species of jellyfish can glow in the dark
Some species of jellyfish possess the incredible ability of bioluminescence, meaning that they can produce light through a chemical reaction in their body. The main reason this is used is as a form of defence; the sudden burst of light can startle predators into leaving the jellyfish well alone. It may also be used as a way to attract a mate.
Approximately 50% of jellyfish species have this ability. The crystal jellyfish (Aequorea victoria) is a well-known example that lives in the northwestern Pacific Ocean.
Jellyfish have been around for over 500 million years
Jellyfish are some of the oldest creatures on the planet! They’re significantly older than trees (385 million years old) and sharks (450 million years old), with evidence suggesting that jellyfish have been around for almost 700 million years.
Jellyfish have managed to live this long, surviving 5 mass extinction events along the way, by adapting to live in a range of environments. They can survive in arctic waters, tropical waters and everything in between.
Jellyfish don’t have brains, hearts, or bones
You read that right: jellyfish don’t have brains! This is due to the fact that they evolved a different type of nervous system called a nerve net, which is spread throughout their body and detects changes in their environment and responds with automatic reflexes.
Similarly, they don’t have a heart or bones because they simply don’t need them! Jellyfish have a hydrostatic skeleton, which relies on the fluid pressure within their bodies to keep their shape, as opposed to a rigid bone skeleton. They are 95% water, and it’s even been reported that because of their make up, they don’t feel pain.
Only some species of jellyfish have eyes
If you’re wondering ‘do jellyfish have eyes?’, you’re in the right place! When you think of a jellyfish, you probably don’t picture two big, round eyes like most other animals, so how do they see? The answer is: most of them don’t.
Instead, they rely on light-sensitive cells called rhopalia that are located around their bells. Box jellyfish, on the other hand, have 6 eye clusters containing 4 eyes in each, for a grand total of 24 eyes.
Jellyfish are found all over the world
Jellyfish are found in every ocean in every corner of the planet, from the coldest waters of the Arctic oceans to the warm, temperate waters of the tropical oceans.
They exist in different water conditions, at different depths from the ocean floor to the surface. They’re even found in some freshwater lakes and ponds!
This range of environments has been crucial to their continued survival, outliving the dinosaurs!
They’re incredibly unique animals that have likely survived in conditions others couldn’t thanks to their lack of bones, a heart, and a brain.
A species of jellyfish is immortal
Just when you thought jellyfish couldn’t get any more interesting, they’ve got another party trick to show us! The immortal jellyfish (Turritopsis dohrnii) has the incredible ability to restart its lifecycle when faced with stress or damage, a process called transdifferentiation, meaning that it can live (theoretically) forever. In comparison, most other jellyfish species can live for anywhere between a few hours or a few months.
You can learn more about the immortal jellyfish in this blog.
Not all jellyfish have the same number of tentacles
Unlike animals like spiders that all have eight legs, there isn’t any uniformity within jellyfish.
The deadly box jellyfish has fish has up to 15 long tentacles, whereas a common moon jellyfish has hundreds of short tentacles that help it to navigate the oceans. As we’ve mentioned, it’s not just the number of tentacles that differs between species – even the colours, lengths, and functions of the tentacles vary hugely.
Jellyfish diet consists of fish and crustaceans
Jellyfish might not look like capable predators, but their stinging tentacles allow them to catch prey with relative ease.
So, what do they eat? They’ll feed on almost anything they can get their mouths around which includes fish, plants and crustaceans.
Interestingly, jellyfish have mouths that also function as a way of removing waste.
Lion’s mane jellyfish is the largest species of jellyfish
The lion’s mane jellyfish (Cyanea capillata) – also known as the giant jellyfish or the hair jelly – is the largest known species of jellyfish. It measures approximately 2 metres in diameter and is usually found in the temperate waters of the Arctic, North Atlantic, and North Pacific Oceans.
Its large size and hair-like tentacles give it the appearance of a lion’s mane.
The largest recorded specimen was found washed up on the shore of Massachusetts Bay in 1870. It had a bell with a diameter of 7 feet 6 inches and tentacles 121.4 feet long – longer than a blue whale and is considered one of the longest known animals in the world.
The Irukandji jellyfish is the smallest species of jellyfish
On the other end of the spectrum, you have the Irukandji jellyfish, which is only the size of a £1 coin. It’s found in the waters surrounding northern Australia, but as you can imagine, they’re difficult to spot.
As well as being considered one of the smallest and most venomous jellyfish in the world!
It’s estimated 150 million people are stung by a jellyfish every year
Despite plenty of people being stung by jellyfish every year, it’s not usually their fault. Jellyfish (as we mentioned) can’t even see to sting you. They sting purely as a defence mechanism when they feel threatened.
In other words, if you avoid them, they’ll avoid you. However, if you can’t avoid a sting, simply rinse it with seawater and then wash with hot water and the sting should get better with time.
If you experience severe symptoms, then you should seek immediate medical care.
A group of jellyfish are called a smack
If you see a group of jellyfish floating around the coast, you’ve seen a smack! That’s right, the collective name for a group of jellyfish is a smack. This is likely due to the severe pain that a sting from a jellyfish will deliver.
While they aren’t typically sociable animals, they can sometimes group together due to ocean currents or when hunting.
Jellyfish have many predators
Despite their venomous defences, jellyfish are not without predators. Tunas, sharks, swordfish, sea turtles, and even some species of salmon are jellyfish’s natural enemies that are known to prey upon jellies.
See jellyfish at Bristol Aquarium
At Bristol Aquarium, we’ve got two species of jellyfish in our Sunken Shipwreck exhibition.
Moon jellyfish (Aurelia aurita)
The moon jellyfish is a common jellyfish around the Atlantic, Pacific, and Indian Oceans, and can be found around the coasts of England, including Bristol. They’re so common because they can survive in temperatures as low as -6°C to as high as 31°C.
Their translucent, floaty appearance gives them their name. Unlike the moon, they produce their own light through bioluminescence.
Sea nettle jellyfish (Chrysaora quinquecirrha)
The sea nettle jellyfish is native to both the Atlantic and Pacific oceans, preferring the warm waters of places like the Caribbean and Mexico.
It differs in colour from dark to light brown, with long, thin tentacles that help it sting and gather its prey. Sometimes, they can even have a star pattern on the top of their bell.
Pacific sea nettle (Chrysaora fuscescens)
Also known as the West Coast Sea nettle, these jellyfish have a powerful nettle-like sting, which any other creature that comes into contact with their tentacles will quickly learn!
This species is native to the northeastern Pacific Ocean, and can be spotted off the coast of British Colombia, and from the West Coast of the USA down to Mexico.
Learn more about jellyfish
If you’ve enjoyed all our fun jellyfish facts so far, you’ll be glad to hear that there’s more where that came from – in this case, at Bristol Aquarium! Book your tickets now to see our jellyfish up close!