Lion's mane jellyfish

The lion’s mane jellyfish is a gentle giant of the cold sea. It has a soft, wobbly, umbrella-shaped body called a bell, and beneath it hang lots of long, flowing tentacles. All those trailing tentacles look just like the shaggy mane of a lion, and that is how this jellyfish got its name.

It is one of the largest jellyfish in the whole world. The bell of a really big one can be wider than a grown-up is tall, and its finest tentacles can stretch out an amazing distance behind it, like silky ribbons drifting in the water. Young ones are a pale orange, and they turn deeper red and purple as they grow up.

Lion’s mane jellyfish live in the cool waters of the north, in the Arctic and the chilly parts of the Atlantic and Pacific Oceans. They are not strong swimmers. They gently squeeze their bell to give a little push, then let the ocean currents carry them along, so they mostly drift near the surface wherever the water takes them.

Its tentacles are covered in hundreds of tiny stinging cells. When a small fish or a speck of drifting sea life bumps into them, the jellyfish catches it and pulls it up to its mouth to eat. The sting is for catching little sea creatures, not for people, and for a swimmer it usually just feels like a nettle prickle. At the beach the rule is simple and kind: look, but do not touch.

Scientists have not yet given this jellyfish a conservation rating, but it is not thought to be in any danger. It has been drifting through the cold seas for a very long time, quietly helping to keep the ocean’s web of life in balance.