I don’t think you’re ready for this jelly!
Still, we’ve got all your jellyfish fact and trivia right here.
Jellyfish are a sight to behold. They are most commonly known for their sting. Other than their stinging tentacles, they are also known for being lazy and useless in the eyes of many people!
But like all creatures on the planet, each one has a specific place and purpose in its ecosystem. Today we are going to learn all about jellyfish.
Boneless Beauties Beneath the Waves!
Jellyfish are one of my favourite animals so this will be a rather enthusiastic look at this mysterious creature.
The jellyfish is shaped like a parachute, with a bell-shaped top (the jelly) and tentacles coming from the centre of the jelly. Most float freely around the water while some are tethered to the ground by stalks.
The tentacles contain stinging cells that jellyfish use to both stun and capture prey as well as ward off any potential predators.
Off the coast of the Atlantic Ocean there are tiny jellies that float right up to the sandy coast. This is also where people swim.
Swimmers are warned against the potential for jellyfish stings but most do not care and swim anyway.
I have swam amidst hundreds of purple jellies in the Atlantic Ocean and have never been stung. You just have to leave them alone, see? They’re like bees. Or anything that stings, really.
They’ll only waste that energy if they’re really threatened. Does the jellyfish look like the type of creature that swims around picking fights? No. they choose to live by the motto Do No Harm And Take No Shit.
And we totally support that.
That said, their stings are not pretty and they hurt like a mofo!
Biology and Evolution
Today we’re going to teach you all about their biology and adaptive traits, and how they turned out the way they did. We’re also going to delve into their reproduction and development, what they eat, and try to answer the ever-controversial question: Are they fish or plant?
Jellyfish, like most of the things that live in the water, are mysterious creatures. For one, they have no hard parts or bones. This means fossilized jellyfish are extremely rare, so it is hard to trace their history and evolution.
Jellyfish are the oldest multi-organ animal on the planet. They are animal, yes. Not a plant. They have been around for at least 500 million years but quite possibly as long as 700 million years.
That’s a pretty long time, considering we only learned how to make fire 800 000 years ago. Some simple math will tell us that this means jellyfish have been around 875 times longer than we have been making fire.
People eat jellyfish in some cultures. They are a delicacy in some Asian countries where they have excess water removed by means of pressing and salting.
Some animals who live in the ocean have light-up features, or bioluminescence. The jellyfish is one of these. Bioluminescence occurs when living beings produce and give off light.
Take a look at this!
Another example of a bioluminescent creature would be the firefly.
This fluorescent green protein is used in research where scientists cross it with specific genes and insert into cells or other organisms.
Since it lights up, it is able to tell the scientist where and how reactions take place.
There are four kinds of jellyfish, officially:
Scyphozoa – True Jellyfish
The true jellyfish has what is called tetra-radial symmetry. This means you could cut the jellyfish in half four times and reveal exact symmetry in these pieces.
The starfish is another example of a radial animal, with symmetry coming to a singular meeting point.
Tentacles grow from the periphery of the bell, with long arms in the centre.
There are about 200 species of scyphozoan.
The main feature of this jellyfish is, well, it’s bell-shaped jelly. This hollow mass is called mesoglea, 95% of which is water.
There is also collagen and some other proteins that take in debris or bacteria. This gelatinous mass is held together by an epidermis. The edges of the bell-shaped jelly is divided into lobes that open and close as the jellyfish propels through the water.
From under the centre of the bell hangs the manubrium: the tip of which is both the mouth and the anus of the jellyfish. Typically there are four arms connected to this.
The mouth opens to absorb nutrients, which go through a central stomach and four gastric pockets.
Hydrozoa – Tiny Jellyfish
Tiny jellyfish are also tetra-radial. They don’t have arms like the scyphozoa.
There are about 2000 species under this umbrella.
Cubozoa – Box Jellyfish
Box jellyfish are known for being very dangerous to people: their stings have been known to cause death, or serious injury at the very least.
They are so named for the rounded or box-shaped bell. They swim more quickly.
There are about 20 species of box jellyfish in the world.
From each of the lower four corners of the “box” hangs a stalk bearing tentacles. Box jellyfish swim faster than true jellyfish because the pulsation of the bell creates a powerful jet.
Box jellyfish each have 24 eyes. Two of these eyes can see colour, while the rest work together to give the jellyfish 360 degree vision. Imagine that!
Staurozoa – Stalked Jellyfish
These jellyfish appear to be upside-down, with a stalk that grows from the tip of their bell.
There are about 50 species of stauozoa.
What do all these jellyfish have in common?
Most do not have a central nervous system, nor do they have a system for breathing (respiration) or circulation (blood).
The epidermis, or the skin that holds the jelly together, absorbs oxygen through itself, and this is how the jellyfish breathes. Therefore they do not need a respiratory system.
There are some nerves in the epidermis allowing them to detect stimuli in their vicinity, while a pacemaker controls how fast they swim, as well as the direction.
They move by means of pulsating their bodies, acting rather like a suction cup.
They release and contract the mesoglea as a means of propulsion. This serves to suck in water, which refills the bell and pushes up against the centre of the body, thereby pushing the jellyfish forward.
They do not have a lot of control over their movement.
More Jellyfish Facts
Most jellyfish tend to drift with the current, while some are active swimmers.
Many species are able to tell between light and dark using their light-sensitive organs calle ocelli.
The stinging cells scientifically are called nematocysts and they are usually located on the tentacles.
All jellyfish are different sizes and shapes. They range anywhere from as tiny as one millimeter in height and diameter (of the bell), while others can grow as big as 2 metres in bell height and diameter.
The Lion’s Mane Jellyfish is the largest jellyfish and the longest animal in the world. Its tentacles grow up to 36 ½ metres in length, or 120 feet.
This is the largest documented size. Their stings are pretty painful but rarely fatal. Another large species is the Nomura jellyfish, which live in Japanese, Chinese and Korean waters.
In late autumn their bodies grow up to 79 inches in diameter and weigh about 440 pounds.
The tiniest jellyfish have more disk-like bells that measure 0.5 mm in diameter with tiny tentacles extending out. These tiny tentacles help the jellyfish move across seaweed or the bottoms of pools.
They cannot be seen without a microscope. They reproduce through fission (splitting in half).
Simply put, jellyfish reproduce similarly to other fish where the sperm fertilizes eggs, producing larva, who then become polyps that bud and eventually transform into adults. Some species skip some of these stages.
Adults release both sperm and eggs into the water, which float freely and then fertilize.
As adults, jellyfish spawn all the time if there is a good and reliable food supply. All of them spawn at around the same time of day, usually at dawn or dusk.
Jellyfish are carnivorous creatures, meaning they eat other animals. Specifically, the jellyfish eats other jellyfish, small fish, fish eggs, crustaceans or plankton. They take in and excrete food from the same place, as the mouth and the anus of the jellyfish are one and the same.
They are passive animals and they collect their prey in the same style, catching it with their tentacles, stunning with the stinging cells and then bring it up to the mouth. As they swim along, expanding and contracting, the expansion enables them to catch more prey.
Jellyfish live in the ocean typically though there are a few specie who live in freshwater. Some, like the tiny jellyfish we mentioned earlier, creep around the ocean floor. Others may take a rest on the seabed of shallow water. Most live well off the ocean floor.
Can You Eat A Jellyfish? Yep!
Like most things on the planet, jellyfish are harvested by humans. They are often fished as a delicacy to eat, while others are farmed or fished for their collagen. This collagen is used in the treatment of rheumatoid arthritis. Some North American companies will harvest jellyfish and export them to Asia.
Only 12 species of scyphozoan jellyfish are harvested and this is mostly in southest Asia, but the American cannonball jellyfish is favoured for its rigid body, and that its toxins are harmless to humans.
It takes 20-40 days to process a jellyfish. First the gonads and mucous membranes are removed, then the umbrella/bell and arms are compressed after being treated with salt and alum.
This process makes the jellyfish crispy and acidic as they only retain 7-10% of their weight this way (remember, 95% of the jellyfish is water).
Jellyfish is served most often with vinegar, sugar or soy sauce.