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Science & Nature • Marine Life

Sea cucumber

Sea cucumbers are marine invertebrates in the class Holothuroidea, within the echinoderm group that also includes sea stars and sea urchins.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

Sea cucumbers are marine invertebrates in the class Holothuroidea, within the echinoderm group that also includes sea stars and sea urchins. They live on the seafloor in saltwater habitats worldwide, from shallow coastal areas to the deep ocean. Many species help recycle nutrients by feeding on organic matter.

Classification and appearance

Sea cucumbers are echinoderms in the class Holothuroidea. They typically have soft, cylindrical bodies and may have tube feet and tentacles around the mouth.

Habitat and distribution

These animals live in saltwater environments in every ocean. They are usually benthic, meaning they live on the seafloor, and can be found from coastal waters to deep-sea habitats.

Feeding and ecological role

Sea cucumbers feed on detritus, small organic particles, and sometimes plankton. By processing sediment and organic matter, they contribute to nutrient recycling in marine ecosystems.

Human use and conservation

Sea cucumbers are harvested in some countries for food and other products. In some areas, heavy harvesting has contributed to population declines and conservation concerns.

Key facts

  • Sea cucumbers are animals, not plants or vegetables.
  • They are echinoderms with soft, elongated bodies and tube feet.
  • Most species live on or near the ocean floor in all world oceans.
  • Many species are scavengers or detritivores that help recycle nutrients.
  • Some species are harvested for food, affecting populations in some regions.
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Canadian context

Sea cucumbers occur in Canadian marine waters, including the Pacific and Atlantic coasts, and are relevant to Canadian fisheries, marine ecology, and conservation discussions.

Frequently asked questions

What is a sea cucumber?
A sea cucumber is a marine invertebrate echinoderm in the class Holothuroidea.
Are sea cucumbers animals?
Yes. Sea cucumbers are animals, not vegetables or plants.
Where do sea cucumbers live?
They live in saltwater environments worldwide, usually on the ocean floor, from shallow waters to the deep sea.
What do sea cucumbers eat?
Most feed on detritus, organic matter, and small particles from the seafloor; some also consume plankton.
How many species of sea cucumber are there?
Sources estimate roughly 1,200 to 1,700 known species.
Why are sea cucumbers important?
They help recycle nutrients in marine ecosystems by processing sediment and organic material.

References

  1. National Wildlife Federation — https://www.nwf.org/Educational-Resources/Wildlife-Guide/Invertebrates/Sea-Cucumbers
    Supports: Echinoderm classification, benthic habitat, feeding, and broad distribution
  2. National Geographic — https://www.nationalgeographic.com/animals/invertebrates/facts/sea-cucumbers
    Supports: Scientific name, approximate species count, habitat range, and classification
  3. Natural History Museum — https://www.nhm.ac.uk/discover/what-is-a-sea-cucumber.html
    Supports: Sea cucumbers as marine animals, class Holothuroidea, and seafloor habitat
  4. NOAA National Ocean Service — https://oceanservice.noaa.gov/facts/seacuke.html
    Supports: Sea cucumbers are animals, saltwater-only distribution, and echinoderm relationship
  5. Britannica Kids — https://kids.britannica.com/kids/article/sea-cucumber/602933
    Supports: Body form, tube feet, feeding, reproduction, and species count
  6. Florida Museum of Natural History — https://www.floridamuseum.ufl.edu/100-years/object/sea-cucumbers/
    Supports: Ecological role in nutrient recycling and harvest pressure