The Lion’s Mane Jellyfish or Cyanea capillata is one of the biggest animals in the oceans and certainly the biggest jellyfish known. In far northern waters, it can grow to 3m across its body with tentacles 100m in length. Those visiting British shores, as they do every year from Spring to Autumn, are smaller but can still be 10m long. Despite these massive proportions, this is an annual animal which starts out life in late winter as a tiny, insignificant item in the plankton. By feeding on other planktonic organisms, it can achieve this massive bulk in a few short months. It has been observed feeding by pulsing its way to the surface and then letting itself sink. As it does so, its tentacles spread out around it like a huge circular net and as it slowly drops through the water column, everything in its way – fish, other jellyfish, plankton and so on – sticks to the tentacles and is consumed. Come the Autumn and declining hours of daylight, the plankton supply has diminished considerably, the seas get very rough and the lion’s mane jellyfish dies.
The Lion’s Mane packs a ferocious sting and a bather meeting up with a large one may be seriously affected. Non-divers are generally horrified at the sight of jellyfish on a beach but underwater, a big specimen of a Lion’s Mane pulsing along powerfully in the sunlight, accompanied as they often are by a shoal of whiting, is an outstanding sight.

The Lion’s Mane Jellyfish or Cyanea capillata is one of the biggest animals in the oceans and certainly the biggest jellyfish known. In far northern waters, it can grow to 3m across its body with tentacles 100m in length. Those visiting British shores, as they do every year from Spring to Autumn, are smaller but can still be 10m long. Despite these massive proportions, this is an annual animal which starts out life in late winter as a tiny, insignificant item in the plankton. By feeding on other planktonic organisms, it can achieve this massive bulk in a few short months. It has been observed feeding by pulsing its way to the surface and then letting itself sink. As it does so, its tentacles spread out around it like a huge circular net and as it slowly drops through the water column, everything in its way – fish, other jellyfish, plankton and so on – sticks to the tentacles and is consumed. Come the Autumn and declining hours of daylight, the plankton supply has diminished considerably, the seas get very rough and the lion’s mane jellyfish dies.
The Lion’s Mane packs a ferocious sting and a bather meeting up with a large one may be seriously affected. Non-divers are generally horrified at the sight of jellyfish on a beach but underwater, a big specimen of a Lion’s Mane pulsing along powerfully in the sunlight, accompanied as they often are by a shoal of whiting, is an outstanding sight.