Sea anemone

Sea Anemones are a group of marine, predatory animals of the order Actiniaria. They are named after the anemone, a terrestrial flowering plant, because of the colourful appearance of many. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia. As cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra.

Anatomy

Sea anemones are polyps attached at the bottom to the surface beneath it by an adhesive foot, called a basal disc, with a column-shaped body ending in an oral disc. Most are from 1.8 to 3 cm (0.71 to 1.18 in) in diameter, but anemones as small as 4 mm (0.16 in) or as large as nearly 2 m (6.6 ft) are known. They can have from a few tens to a few hundred tentacles.

Distribution and habitat

Sea anemones are found from the tidal zone of all oceans to depths of more than 10,000 metres (about 33,000 feet). Some live in brackish water. They can be found in a wide range of environments, including sponges, shells and floating in the open ocean.

Reproduction

Sea anemones can reproduce by both sexual and asexual means. They can also reproduce by budding, in which a portion of the base or side gives rise to a new individual.

Relationship with humans

Sea anemones are sometimes kept in reef aquariums; the global trade in marine ornamentals for this purpose is expanding and threatens sea anemone populations in some localities, as the creatures are removed.

See also

• Coral reef
• Cnidaria
• Anthozoa

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