Sea Anemone

Actiniaria
Image by Nhobgood.

Sea anemone are a group of water dwelling, predatory animals of the order actiniaria; they are named after the anemone, a terrestrial flower.

As cnidarians, sea anemone are closely related to corals, jellyfish, tube-dwelling anemone, and hydra. A sea anemone is a polyp, attached at the bottom to the surface beneath it by an adhesive foot (pedal disk), with a column shaped body ending in an oral disk. The mouth is in the middle of the oral disk, surrounded by tentacles armed with many cnidocytes (cells that function as a defense and as a means to capture prey).

When the ‘hair’ is touched, it mechanically triggers the cell explosion; a harpoon-like structure which attaches to organisms that trigger it, injecting a dose of poison in the flesh of the aggressor or prey. This gives the anemone its characteristic sticky feeling.

Anemones tend to stay in the same spot until conditions become unsuitable (prolonged dryness, for example) or a predator attacks them. In that case anemones can release themselves from the substrate and use flexing motions to swim to a new location.