Subscribe Now! National Geographic Magazine $15
Visit our Online Shops

Sign up for free

Newsletters

Once a month
get new photos
and expert tips.

Sea Anemone
Actiniaria

Photo: a brilliant purple sea anemone nestles in among soft corals and other reef inhabitants
A brilliant purple sea anemone
Photograph by David Doubilet

Sea Anemone Profile

The ornately colored sea anemone (uh-NEM-uh-nee) is named after the equally flashy terrestrial anemone flower. A close relative of coral and jellyfish, anemones are stinging polyps that spend most of their time attached to rocks on the sea bottom or on coral reefs waiting for fish to pass close enough to get ensnared in their venom-filled tentacles.

Their bodies are composed of an adhesive pedal disc, or foot, a cylindrical body, and an array of tentacles surrounding a central mouth. The tentacles are triggered by the slightest touch, firing a harpoon-like filament into their victim and injecting a paralyzing neurotoxin. The helpless prey is then guided into the mouth by the tentacles.

There are more than 1,000 sea anemone species found throughout the world’s oceans at various depths, although the largest and most varied occur in coastal tropical waters. They run the full spectrum of colors and can be as small as half an inch (1.25 centimeters) or as large as 6 feet (1.8 meters) across.

Some anemones, like their coral cousins, establish symbiotic relationships with green algae. In exchange for providing the algae safe harbor and exposure to sunlight, the anemone receives oxygen and sugar, the bi-products of the algae's photosynthesis.

They form another, more famous symbiotic alliance with clownfish, which are protected by a mucus layer that makes them immune to the anemone's sting. Clownfish live within the anemone’s tentacles, getting protection from predators, and the anemone snacks on the scraps from the clownfish’s meals.

Fast Facts

Type: Invertebrate
Diet: Carnivore
Size: Diameter, 0.5 in to 6 ft (1.25 cm to 1.8 m)
Did you know? Some species of sea anemone can live 50 years or more.
Size relative to a tea cup:
Illustration of the animal's relative size

Multimedia

Sea Creature Features

Photo: Seal

Underwater Ireland

Put down that pint and go diving off the coast of Ireland. See the underwater surprises that await you in this multimedia feature.

Photo: Sea anemone

Photo of the Day: Anemone Enemies

Watch sea anemones, sponges, and coral in a slow-motion turf battle in the nutrient-rich waters of California's Monterey Bay.

Photo: Sea anemone

Photo of the Day: Fire Arms

Go 12,000 feet (3,657 meters) deep in the ocean off California and see orange-tinted sea anemones awaiting a hapless victim.

Photo: Green anemone

Photo of the Day: Green Meanie

The sting of a green anemone—seen here in the waters of the Channel Island National Marine Sanctuary in California—is harmless to humans.

Photo: Sea otter

Virtual World: Monterey Bay

Dive down into the diversity of life in California's Monterey Bay National Marine Sanctuary.

Other Sea Creatures

Map: Locator map for the sea anemone
 Sea Anemone range

Special Advertising Sections

Photo: Feeding a horse

Share Your Life Dream

One woman fulfilled her dream of helping injured horses. What's your dream?

Photo: Cosmic rays

Innovation in Education

Are you a math or science whiz? Take our quiz.

Invertebrates Right Rail

Get the Latest Headlines

Photo: Blue poison dart frogs

Make us your online news source.

Get Invertebrate Pictures

Photo: Giant octopus

Get your daily dose of photos

For Kids!

Photo: A cartoon dog

It's no stretch to find fun facts on our Kids site!

Gifts to Inspire Adventure

Image: Swiss Army knife

Encourage your loved ones to get out and explore.