Jellyfish: The ancient animal with no brain, heart or bones

The jellyfish is one of the ocean's most dreamlike animals: a transparent little bell drifting through the water with tentacles trailing gently behind. Yet it is a very ancient animal — jellyfish appeared on Earth hundreds of millions of years ago. Let's meet it.

Its body

A jellyfish's body is remarkable: it has no brain, no heart and no bones, and most of it is water — which is why it looks almost transparent. Its body is like a bell with long tentacles hanging from the rim. It swims by pulsing the bell, looking both elegant and slow. Because its body is nearly water, it drifts in the sea with very little effort.

How it catches food

The tentacles carry many tiny stinging cells that fire threads to catch small fish and shrimps. When a stinging cell touches prey it "fires", paralysing the animal, which is then moved to the mouth. Because some jellyfish stings hurt people, it is best to keep your distance at the seaside and never touch them with your hands.

Why it matters

Simple as it looks, the jellyfish is an important link in the ocean food chain: it eats small fish and shrimps, and is itself food for sea turtles, ocean sunfish and others. Some sea turtles feed on little else. So this "little bell with no brain" plays a role in the ocean that is impossible to ignore.

A note for grown-ups

You could talk with a child about how you can live without a brain — the jellyfish has managed it for hundreds of millions of years with the simplest of bodies. Helping a child see that "simple" does not mean "inferior", and that every kind of life has its own wisdom, is a lovely idea. At the seaside, do tell your child: look, but do not touch.