Article Lead Image

What a jellyfish sting looks like in microscopic slow motion

Here's how the specialized stinging cells in a jellyfish’s tentacles inject you with venom. Have fun at the beach!


Marissa Fessenden


Posted on Aug 18, 2014   Updated on May 30, 2021, 6:21 pm CDT

Nothing ruins a beach day like a jellyfish sting. But if you’ve ever wondered why brushing past their venomous tentacles can be so painful, then check out this video.

Destin, creator of the Smarter Every Day videos on YouTube, shows us how the specialized stinging cells in a jellyfish’s tentacles inject you with venom. 

Jellyfish and their relatives the anemones have stinging cells called cnidocytes. Inside each of these cells lies coiled “garden hose” structures called nematocysts. When the cell is activated by a brush with, oh, say a human leg, the hose structure shoots out and injects venom, much like a hypodermic needle or harpoon. Except each tentacle has thousands of tiny needles or harpoons. 

To see these terrifyingly effective weapons in action, Destin took a high speed camera to a venom biologist, Jamie Seymour, at the James Cook University in Australia. (If you want to study venom, do it in Australia, home to some of the world’s most venomous animals.) Seymour set up an anemone tentacle under a microscope: “It’s the same process!” he explains. He likens it to finding out how bullets work by looking at a Glock instead of an AK-47. They triggered the nematocysts to fire with small electrical shocks.

The camera managed to capture a delayed venom ejection after one of the nematocysts deployed. Seymour said this was the first time he’d observed such a delay because previously he didn’t have the technology to see it. “This is the sort of stuff I get up in the morning for,” he says. “It’s the joy of seeing something that nobody else has ever seen before.”

Oh, and while we are talking about jellyfish stings, you should know that peeing on the wound is not a great idea. Don’t scratch or rub either, lest you trigger the undeployed nematocysts and release more venom. Vinegar will work for some North American jellyfish species, but time seems to be your best bet. 

Photo by the_tahoe_guy/ (CC BY 2.0)

Share this article
*First Published: Aug 18, 2014, 10:57 am CDT