Cnidarians such as jellyfish and corals have stinging cells called nematocysts. When touched they eject barbed threads tipped with poison.


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Box Jellyfish: World's Most Venomous Sea Creature

Most jellyfish are more bothersome than threatening, but the box jellyfish is so poisonous you might not make it out of the water alive.

Stinging 'Sea Lice' Invading Atlantic Beaches

Sea lice aren't actually lice — they're jellyfish — but they're no fun when they get in your bathing suit.

Jellyfish Don't Have Brains, But They Still Sleep

Don't think you have much in common with a jellyfish? What researchers just discovered may surprise you.

As Oceans Acidify, Vulnerable Baby Fish Lose Poisonous Protectors

Baby fish rely on jellyfish to protect them from predators, but that delicate symbiosis is at risk as seawater CO2 levels rise due to human actions.

A Bright Side for Coral Reefs?

Corals reefs have had a rough last few decades, but researchers have discovered a few reefs that are doing better than expected. And they're eager to learn why.

An 'Impossible' Coral Reef System Discovered at Amazon River Mouth

How can a rich ecosystem exist beneath water as muddy as that of the Amazon River's plume? The surprising discovery all has to do with physics and density.

How to Treat a Jellyfish Sting

You're going on vacation to a place where jelly fish stings are a common occurrence and you want to know how to treat a jellyfish sting. This article will tell you how to treat a jellyfish sting.

Do jellyfish have the deadliest venom in the world?

As you observe jellyfish twirl underwater, it's difficult not to be mesmerized by their graceful movements. But if their tentacles touch your skin, you'll regret being anywhere near these gelatinous blobs.

How Coral Reefs Work

How do coral polyps mere millimeters in length form the world's largest living structures? Will these giants of the sea last much longer if the present rate of destruction continues?

How Jellyfish Work

Although jellyfish have been around for over 650 million years, they're still very mysterious. Learn the all about the fascinating jellyfish life cycle.