Sea anemones are invertebrates that look like flowers, for which they are named.
They’re animals, however, not plants; related to coral and jellyfish, sea anemones are polyps made up of a soft cylindrical stalk of a body topped with an oral disc surrounded by tentacles. At their base, they sport a single adhesive foot, called a basal disc, which they use to attach to underwater surfaces like rocks or shells. Anemones can have anywhere from a dozen to a few hundred tentacles.
Numerous species of sea anemones are found throughout the oceans at various depths. These cnidarians come in all colors, decorating a tide pool or reef like a garden of wildflowers. Most anemones usually stay in the same spot until conditions become unsuitable.
Anemones are known to form symbiotic relationships with other animals. They may attach to the shell of a crab and hitch a ride to another part of the ocean, for example. The most famous alliance is with clownfish. By building up a protective mucous coating, the clownfish is immune to the stinging cells of the anemone. The clownfish makes its home within the anemone’s tentacles, enjoying protection from predators; in return, the anemone gets to eat the leftovers from the clownfish’s meals.
At the National Aquarium, you can see 10 different species of sea anemones throughout the exhibits.
Anemones are carnivores. Some feed on tiny plankton, and others feed on fish. The anemone has stinging tentacles, which are triggered by the slightest touch, firing a harpoon-like filament (called a nematocyst—the same thing that causes a jellyfish sting) into their victim and injecting a paralyzing neurotoxin. The helpless prey is then guided into the mouth by the tentacles.
The anemone has a single opening in the center of the oral disc, where food goes in and digested food comes back out.
At the Aquarium, we feed them pieces of shrimp and fish, krill, and brine shrimp.
Most anemones are small, but some can grow as large as 6.5 feet in diameter!
Anemones are found worldwide in all marine habitats, at various depths. They can be found in a variety of temperature ranges from the cold water of the north Pacific to the warm water of the Caribbean. Their ability to live at various depths ranges from being close to the surface in the tidal zone to depths of over 1.8 miles (3,000 meters).
The majority of anemone species are considered not threatened, but there are a few species that are vulnerable, and if the health of the oceans continues to decline we may see more species become vulnerable or even extinct.
Many species of fish, sea stars, and snails will opportunistically feed on anemones. Sea turtles have been known to feed on them, as well. The stinging cells of the anemone help to ward off some predators, but if an animal is big enough or clever enough, it can still make a meal out of an anemone.
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