Pity the small fish snagged by a sea anemone. Blundering into the waving tentacles, the fish is stung by hundreds of tiny harpoons shot out from stinging cells, each one loaded with potent venom. It is paralysed and moved towards the anemone’s ‘mouth’, which lies in the centre of its tentacles and also doubles as its anus. The fish is swallowed and , but its ignominious fate doesn’t end there. The anemone’s internal cavity (which passes for its stomach) is also lined with thousands of stinging cells so that even after it’s been swallowed, the fish continues to be stung.

The sea anemone is a member of a 10,000-strong group of simple animals called the cnidarians, whose ranks also include