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Science & Nature • Marine Biology

Sea anemone

Sea anemones are marine invertebrate animals in the order Actiniaria, closely related to corals and jellyfish.

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

Sea anemones are marine invertebrate animals in the order Actiniaria, closely related to corals and jellyfish. They typically have a soft cylindrical body, a central mouth, and rings of venomous tentacles used to capture prey. These animals live in oceans worldwide and are often attached to rocks, shells, or other hard surfaces.

Description

Sea anemones are soft-bodied marine animals with a cylindrical column, a mouth surrounded by tentacles, and a basal disc for attachment. Their flower-like appearance has led to the common name, but they are invertebrates. The body plan consists of a soft cylindrical polyp with tentacles and a basal disc.

Habitat and distribution

Sea anemones occur in both shallow coastal waters and deeper ocean habitats worldwide. Species diversity is especially high in tropical waters, but anemones are also found in colder seas. They are marine animals that live in oceans around the world.

Feeding and defence

Sea anemones are predatory animals that use venomous tentacles to capture small fish and other marine animals. The same stinging cells that immobilize prey also help defend them from threats.

Ecological relationships

Sea anemones can provide shelter or protection for other marine animals, including species that live among or near their tentacles. They are part of reef and coastal ecosystems and interact closely with other cnidarians and fish.

Key facts

  • Sea anemones are animals, not plants, despite their flower-like appearance.
  • They are cnidarians, placing them in the same broader group as corals and jellyfish.
  • Their tentacles contain stinging cells used to immobilize prey.
  • Many species attach to hard surfaces with a basal disc, though some live in sediment or float.
  • More than 1,000 species are found in oceans around the world.
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Canadian context

Sea anemones occur in Canadian marine waters, including the Pacific and Atlantic coasts, making them part of Canada’s coastal marine biodiversity. They are also familiar to Canadians through aquariums, marine science education, and intertidal ecosystems.[3][11]

Frequently asked questions

Are sea anemones plants or animals?
They are animals, specifically marine invertebrates in the phylum Cnidaria.
What do sea anemones eat?
They feed on small animals such as fish and other marine organisms that they capture with their tentacles.
Are sea anemones related to jellyfish?
Yes. Sea anemones are closely related to jellyfish and corals because all are cnidarians.
How many species of sea anemone are there?
There are more than 1,000 known species worldwide.
How do sea anemones attach to surfaces?
Many use a basal disc, or adhesive foot, to anchor themselves to rocks, shells, or other hard surfaces.

References

  1. National Aquarium — https://aqua.org/explore/animals/anemones
    Supports: Body form, basal disc, attachment to surfaces, and relationship to corals and jellies.
  2. National Geographic — https://www.nationalgeographic.com/animals/invertebrates/facts/sea-anemones
    Supports: Classification, body structure, habitat, species diversity, size range, and prey capture with venomous tentacles.
  3. Britannica Kids — https://kids.britannica.com/kids/article/sea-anemone/390115
    Supports: Animal classification, worldwide distribution, attachment behaviour, and relatedness to jellyfish.
  4. Blue Planet Aquarium — https://www.blueplanetaquarium.com/blog/6-fun-facts-about-sea-anemones/
    Supports: Ecological role as habitat and refuge for other animals.