Jellyfish, also known as jellies, are a gelatinous free swimming marine animal, consisting mostly of water and protein, found in oceans around the world. They can be found at all depths. Some species also inhabit fresh water environments.
Jellyfish are characteristically an umbrella shape. They can be large (as large or larger than a human) and very bright in colour or very small (the smallest are known to be the size of a pin head) and almost impossible to see with the naked eye. Many are transparent or semi transparent.
The largest known species of jellyfish is the lion’s mane jellyfish. A specimen (Arctic Lions mane) with a bell measuring 2.3 metres (7'6") around and tentacles 36.5 metres (120') in length was found washed up in Massachusetts Bay in 1870. To date this has been the largest jellyfish found on record.
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| Lions mane jellyfish |
They are the oldest multi-organ species known to exist, having been around for at least 500 million years (probably closer to 700 million). That makes them older than the dinosaurs!!!
And.... despite being called jelly'fish' they aren't actually fish at all. Most species of jellyfish don't have eyes. Nor do they have brains or a central nervous system!! They have a nerve net instead which is a loose network of nerves located in their skin. They also don't have a respiratory system so they receive oxygen via diffusion through their thin skins. They feed on plankton.
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| Jellyfish bloom |
Jellyfish have tentacles which sting. Some species have stings which can kill or are extremely painful, like the transparent and hard to see box jellyfish which has the deadliest venom in the animal kingdom. There have been at least 5,568 recorded deaths since 1954 from box jellyfish stings. The box jellyfish's tentacles have around 500,000 tiny harpoon shaped needles that inject venom into the victim. Fortunately though most jellyfish stings are harmless to humans.
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| Australian Spotted jellyfish |
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| Medusa jellyfish |
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| Flower-hat jellyfish |
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| Nomura jellyfish |
