Most Dangerous Jellyfish

For an animal (just) that is 95% water, has no brain and eats / defecates out of the same opening the jellyfish have a surprisingly complex and effective weapon at their disposal. Most species have tentacles loaded with stinging cells called nematocysts. So, keep on reading to find out the most dangerous jellyfish.

5. Sea Nettle (Chrysaora)

The Sea Nettles are common on both coasts of North America. They are probably best known around the Chesapeake Bay area of the US East coast. Here they aggregate to forming huge blooms (that’s the technical term for a bunch of jellyfish) during the summer months becoming a menace to swimmers.

4.Lion’s Mane Jellyfish (Cyanea capillata)

The lion’s mane jellyfish is the largest species known to man. With a bell reaching up to 8 ft (2.5m) or more across and tentacles trailing over 100 ft (30m) these monster jellies can weigh around a quarter ton.

They also occur in large swarms meaning a convergence of these on your local beach is going to put it out of bounds. The lion’s mane is a coldwater species and can be found throughout the North Atlantic, including the UK. 

3. Portuguese Man o’ War (Physalia physalis)

Strictly speaking the Portuguese Man o’ War, or bluebottle, is not a true jellyfish. It isn’t actually even a single animal. It is actually a whole colony of organisms working together in peace and harmony. The name comes from the air filled bladder that acts as a float and sail – this was thought reminiscent of the 17th century naval ships called men-of-war.

2. Irukandji Jellyfish (Carukia barnesi)

What the Irukandji jellyfish lacks in size it makes up for in the power of its venom. The name is derived from the Irukandji people of North Australia, as this is where the jellyfish was first observed. However, it appears to be much more widespread than this with specimens allegedly found as far away as the British Isles.

1. Box Jellyfish (Chironex fleckeri)

It seems to go without saying that the meanest, most poisonous, and deadliest of all jellyfish inhabits Australia. The variety of box jellyfish known as the sea wasp or marine stinger is widely regarded as one of the most deadly creatures on earth.

Along with other box jellies they have been responsible for at least 5,568 deaths recorded since 1954. The Australian variety causes around 1 death a year on average with a further 100 in South East Asia.


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