The Lion’s Mane Jellyfish: A Giant with 1,200 Tentacles Weighing Over a Ton

If you were asked to name a giant of the oceans, the blue whale would probably be the first creature that comes to mind. Today we turn our attention to a very different but equally impressive being: the lion’s mane jellyfish.

Cyanea capillata

Primarily inhabiting the cold waters of the Arctic Circle, as well as the North Pacific and North Atlantic, Cyanea capillata is regarded by the Guinness World Records as the largest jellyfish in the world, with specimens weighing over a ton and measuring more than two meters in diameter.

Its “lion’s mane” consists of roughly a thousand tentacles that can extend beyond thirty meters. Generating large quantities of neurotoxins, they enable it to capture a variety of prey, including small fish, zooplankton, and ctenophores.

If the sting of C. capillata typically causes blisters, irritation and muscle cramps, in the most severe cases it can affect the functioning of the respiratory and cardiac systems. Even specimens that have stranded for a long time remain venomous.

This fascinating creature lies at the heart of one of Sir Arthur Conan Doyle’s Sherlock Holmes adventures from 1926: The Lion’s Mane, in which the giant jellyfish kills a man and his dog and grievously wounds another.

The Largest Jellyfish in the World?

Captured off the coast of North America in 1870, the largest known specimen of C. capillata is thought to have measured 2.3 meters in diameter, with tentacles extending over 37 meters. This claim has been debated by many scientists, who today regard Nomura’s jellyfish as the largest known.

Among its relatives, Nomopilema nomurai (Nomura’s jellyfish) can also exceed two meters in diameter and weigh more than 200 kilograms, primarily in the Sea of Japan. Its remarkably rapid growth today makes it a nuisance for local fishermen.

At the opposite end of the spectrum are the various “Irukandji” jellyfish species. Not exceeding 5 centimeters in diameter and possessing only four tentacles, they are among the most venomous creatures in the world, with stings potentially deadly to humans.