Getting stung by a jellyfish can be a miserable experience. But how can one little invertebrate cause such a big pain?
The answer, it turns out, is even more gruesome than you might think.
As Destin Sandlin, host of the YouTube channel "Smarter Every Day," explains in this fascinating viral video (see above), jellyfish have microscopic, venom-loaded stinging capsules called nematocysts on their bodies.
"They're like little hypodermic needles," Sandlin says, "and when you're swimming and those hypodermic needles brush up against your body, they stab into you and inject venom. It's insane."
To show exactly what nematocysts look like and how they work, Sandlin -- armed with a microscope and high-speed camera -- heads to Queensland, Australia. There Jamie Seymour, an associate professor at James Cook University and an expert on venomous animals, puts the tiny needles under the spotlight.
Venom spurts from a nematocyst of a sea anemone. According to Seymour, the action of nematocysts in sea anemones and jellyfish -- both of which belong to the phylum Cnidaria -- are very similar.
Seymour, for one, is plenty impressed by the view under the microscope. "This is real science," he says. "This is the sort of stuff I get up in the morning for."
(Scroll to 2:12 in the video to see the nematocysts do their dirty work.)