Some species burrow in soft sediment and lack a basal disc, having instead a bulbous lower end, the physa, which anchors them in place. Some are very large Urticina columbiana and Stichodactyla mertensii can both exceed 1 metre (3.3 ft) in diameter and Metridium farcimen a metre in length. Most are from 1 to 5 cm (0.4 to 2.0 in) in diameter and 1.5 to 10 cm (0.6 to 3.9 in) in length, but they are inflatable and vary greatly in dimensions. 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 trade depends on collection from the wild.ġ. Tentacles 2. Mouth 3. Retracting muscles 4. Gonads 5. Acontial filaments 6. Pedal disk 7. Ostium 8. Coelenteron 9. Sphincter muscle 10. Mesentery 11. Column 12. PharynxĪ typical sea anemone is a sessile polyp attached at the base to the surface beneath it by an adhesive foot, called a basal or pedal disc, with a column-shaped body topped by an oral disc. Sea anemones also breed asexually, by breaking in half or into smaller pieces which regenerate into polyps. The resulting fertilized eggs develop into planula larvae which, after being planktonic for a while, settle on the seabed and develop directly into juvenile polyps. Sea anemones breed by liberating sperm and eggs through the mouth into the sea. Some species of sea anemone live in association with hermit crabs, small fish, or other animals to their mutual benefit. In many species, additional nourishment comes from a symbiotic relationship with single-celled dinoflagellates, with zooxanthellae, or with green algae, zoochlorellae, that live within the cells. They are armed with cnidocytes (stinging cells). The tentacles can be retracted inside the body cavity or expanded to catch passing prey. The polyp has a columnar trunk topped by an oral disc with a ring of tentacles and a central mouth. Unlike jellyfish, sea anemones do not have a medusa stage in their life cycle.Ī typical sea anemone is a single polyp attached to a hard surface by its base, but some species live in soft sediment, and a few float near the surface of the water. As cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra.

Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia.

Because of their colourful appearance, they are named after the anemone, a terrestrial flowering plant. Sea anemones are a group of predatory marine animals of the order Actiniaria.

Anemona mediterraneo