Which animal defends itself by turning itself inside out?

Deep beneath the ocean, there’s a family of animals with spiny skin. Most people know about the starfish and the spiny sea urchin, but few people know about the ugliest member of the family, the sea cucumber. But out of all the members of the spiny-skinned family, it’s the sea cucumber that has one of the most exciting responses to danger!

A sea cucumber isn’t much to look at. They look a bit like a long, warty potato or cucumber, and they don’t move very much. Instead, they drift along the bottom of the ocean on the currents, eating any plankton or dead matter that passes by the tentacles around their mouths.

Sea cucumbers also breathe in a strange fashion. They take oxygen from the water just like fish do, but instead of using gills, sea cucumbers have long hairlike strands just inside the anus that take oxygen from the water. These strands are called the respiratory tree. To breate, a sea cucumber has to take water in through its bum and then squirt it back out again.

But if a sea cucumber is threatened, you’ll see some real action. At a sign of danger, a sea cucumber shoots the fibres of its respiratory tree out of its anus! With luck, predators will get tangled up in the intestines, or poisoned by a toxic chemical that is sometimes released at the same time. If the intestines are unharmed, the sea cucumber sucks them back up, but if they are damaged or eaten, new ones will grow back in a few weeks!