The Incredibly Simple Complexity of the Long Enduring Jellyfish

A recent episode of the KQED science series “Deep Look” takes a look at the very simple jellyfish who, despite having no ability to think, see or hear, has one of the most complex and effective systems to capture prey and an uncanny ability to survive as a species for millions of years.

Jellyfish don’t have a heart, or blood, or even a brain. They’ve survived five mass extinctions. And you can find them in every ocean, from pole to pole. What’s their secret? Keeping it simple, but with a few dangerous tricks. Jellyfish sting to paralyze their prey. They use special cells called nematocysts. Jellyfish don’t have a brain or a central nervous system to control these stinging cells, so each one has it’s own trip wire, called a cnidocil. When triggered, the nematocyst cells act like a combination of fishing hook and hypodermic needle. They fire a barb into the flesh of the jellyfish’s prey at 10,000 times the force of gravity – making it one of the fastest mechanisms in the animal kingdom. As the barb latches on, a thread-like filament bathed in toxin erupts from the barb and delivers the poison.