Animal · Indonesia, Philippines, China
Sea cucumber
Holothuroidea — the name this animal has in the language scientists everywhere share.
The sea cucumber is a soft, sausage shaped animal that creeps slowly over the sea floor and is a close relative of the starfish. It has no brain and no eyes, but one of the strangest defences in the whole ocean.
Picture credit: David Burdick / NOAA (Public domain) · seanpmyers (CC0) · Wikimedia Commons
Where does the sea cucumber live?
Home: Sandy and muddy sea floors, from shallow reefs to the deep.
In the wild it lives in these countries: Indonesia, the Philippines, China, Japan, Australia, Madagascar.
The short profile
Fully grown: most kinds are 10 to 30 cm long. It weighs about 0.3 kilograms. On the menu: tiny creatures it filters out of the water.
The story behind it
A sea cucumber eats like a vacuum cleaner: a ring of sticky tentacles around its mouth pushes sand and mud inside, and the tiny scraps of food in it are digested on the way through. What comes out at the other end is clean sand, so reefs and sea floors stay healthier because of these animals. When a crab or a fish attacks, many species shoot out sticky white threads that tangle the attacker, and some even push out part of their insides and grow them back within a few weeks. They also take in oxygen through their rear end, pumping water in and out of two branching tubes inside the body. There are about eighteen hundred kinds, from a few millimetres to more than a metre long, and in many countries they are caught and dried as an expensive food.
Find it on the globe
Sea cucumber is there as a tiny animated figure that breathes and looks around. From far away the planet is only a blue ball; detail arrives as you zoom in, and this one appears once you are close enough. Open it on the globe.
It sits at its real coordinates, not near them — the same numbers listed in the facts above. Switch off the layer for this kind of place and it disappears again; the buttons for that are down the right-hand edge.
Questions children ask
Is a sea cucumber a plant?
No, it is an animal, even though its name and shape sound like a vegetable. It belongs to the same group as starfish and sea urchins, and it moves on rows of tiny tube feet.
What does a sea cucumber eat?
It swallows sand and mud and digests the tiny bits of dead plants and animals in them. Clean sand comes out at the other end, which is why sea cucumbers are called the earthworms of the sea.
How does a sea cucumber defend itself?
Many species shoot sticky white threads out of their rear end to glue up an attacker. Some go further and push out part of their guts, which grow back again in a few weeks.
Where these numbers come from
Every figure on this page was checked against public reference sources before publication. Where sources genuinely disagree, the text says so.
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