Scientists have discovered jellyfish fossil snapshots in rocks believed to be more than 500 million years old. That makes them even older than dinosaurs!
They don’t have a heart, lungs or a brain either! So how does a jellyfish live without these vital organs? Their skin is so thin that they can absorb oxygen right through it, so they don’t need lungs. They don’t have any blood so they don’t need a heart to pump it. And they respond to the changes in their environment around them using signals from a nerve net just below their epidermis - the outer layer of skin - that is sensitive to touch, so they don’t need a brain to process complex thoughts.
Jellyfish often look like a bell with tentacles all around the edge or hanging off the bottom. The shape of this bell is called a medusa because it looks like the evil Medusa in Greek mythology - a woman who had offended the goddess Athena who then changed her hair into snakes and made her face so hideous it turned people into stone. Medusa is also the word for jellyfish in many other languages including Greek, Hebrew and French.
Imagine if you could just split in half and create a second version of yourself? If you cut a jellyfish in half, the pieces of the jellyfish can regenerate and turn into two new jellies.
Photo: T3 Media/Nat Geo
The beroid comb jellyfish has hundreds of rows of “teeth” made of tiny hairs that can pierce, tear and pull their prey into their stomachs.
Photo: Howard Hall
In 1991, moonfish jellyfish travelled into outer space on the Space Shuttle Columbia so that scientists could examine how microgravity affected them. The jellyfish multiplied in space. When they came back to Earth, the scientists discovered that the space-born jellyfish couldn't figure out how to deal with gravity.
Even though some jellyfish have very long tentacles, they never get tangled up or sting them. That’s because the tentacles are very slippery and only sting other species of jellyfish.
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The lion’s mane jellyfish is the world’s largest jellyfish species. It can have tentacles that are over 27 meters long - longer than the size of the blue whale which is the biggest mammal in the world!
You might think that a gaggle of geese, a murder of crows, or a clowder of cats sounds interesting, but jellyfish groups have even better names. A group of jellyfish - which can include up to 300,000 jellyfish - is called a “bloom,” a “swarm” or a “smack.”
Jellyfish are between 85% and 98% water. If they wash up on the beach they’ll almost disappear as their water evaporates.