Sea Anemones are benthic sessile polyps without a skeleton. They are solitary; with the exception of one colonial species, Cereus herpetodes, which is known from Chile. The proximal end of the sea anemone is either rounded, in which case the species is buried in soft substrate, or forms a more or less well developed flat pedal disc, which it uses to attach to hard substrate. The column is smooth or provided with hard structures such as verrucae, tenaculi, tubercles, vesicles, marginal spherules, marginal pseudospherules, or marginal projections.
The oral disc (at the distal end) is usually circular; in some cases it can be drawn out into lobes (eg: Anthologa achates). The tentacles are generally simple, hollow, and usually arranged in hexamerously alternating cycles. They arise from the margin and/or the oral disc, and nearly never possess spherical tips. Some species possess special fighting tenacles that can be everted or retracted; they bear large amounts of special cnidae used for defense. Colour and markings of the animals are highly variable.
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