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Sea Cucumber

Sea Cucumber Facts

Size 4-12 inch (10-30 cm)
Speed Unknown
Weight Unknown
Lifespan 5-10 years
Food Plankton
Predators Starfish, fish, crabs
Habitat In oceans worldwide
Phylum Echinodermata
Class Sea cucumbers
Scientific name Holothuroidea
Characteristics Long, worm-like animal

Main Characteristics

Sea cucumbers are not a kind of vegetable, but animals. They are named sea cucumbers because of the shape of their body, which resembles a cucumber. There are more than 1,200 species of sea cucumbers. Most of the time they live on the ground of the sea.

Sea Cucumber Sea Cucumber - Photo: Ethan Daniels/Shutterstock

Distribution and Habitat

Where do Sea Cucumbers Live?

Sea Cucumbers live on coral reefs but also in the deep sea. In depths of 4-5.5 miles (8-9 km), sea cucumbers make up about 90% of the “biomass” (= mass/amount of living creatures per sector).


Life Style

Sea Cucumbers Are Sociable

The red strawberry sea cucumber lives in groups of up to 93 animals per square feet (1,000 animals per square meter). In their home region New Zealand such colonies are also called strawberry fields.

Sea Cucumber Sea Cucumber - Photo: unterwegs/Shutterstock

Anatomy and Appearance

How Big Do Sea Cucumbers Grow?

There are about 1,200 species of sea cucumbers. The smallest is 0.1 inch (3 mm) long and the longest 3-6.5 feet (1-2 meters) with a diameter of 9.4 inch (24 cm).

How Do Sea Cucumbers Breathe?

Sea cucumbers have a unique way to breathe. They have two respiratory “trees” that branch off their cloaca into their body. The animals breathe by sucking in water through their anus and distribute it into the treelike branches in order to retrieve the oxygen from it.

Sea Cucumber Sea Cucumber - Photo: Erin Wildermuth/Shutterstock


Enemies and Threats

How Do Sea Cucumbers Defend Themselves?

The respiratory system of the sea cucumber is quite unusual – or to put it more bluntly: disgusting for us humans. The sea cucumber’s manner of defense is equally nasty: It ejects its intestines. Who would not be confused by this? Enemies are stunned for a little while until they understand what’s going on – enough time for the sea cucumber to make an escape. Sometimes the sea cucumber also ejects its intestines to get rid of parasites. It simply reproduces itself afterwards (!). Another method of defense is to emit slime which is so sticky that you need a knife to scrape it off.

Sea Cucumber Sea Cucumber - Photo: e2dan/Shutterstock

Importance for the Ecosystem

Sea cucumbers are capable of "bioturbation." The word "turbation" is Latin and means turbulence. And that is exactly what the animals do. They churn up the seabed when feeding. To be more precisely, they swallow the sand and feed on the algae that live in it. In the end, well ventilated and clean sand comes out “at the other end”. Sea cucumbers can also be called earthworms of the sea because they loosen and improve the soil. They also enrich the water with important nutrients that help corals grow and ensure that the water is less acidic.


Female sea cucumbers eject their eggs into the water and the males do the same with their semen. The eggs get fertilized by the semen. Some sea cucumber species can also reproduce by fission.

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