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A 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. 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.
As it does so, some of the tentacles grip the rim and pull the tube closed behind it, effectively making it disappear from view. The tube is normally a permanent home, but if the anemone is disturbed from below, as by a burrowing sea urchin, it can eject itself from its tube, move to a new location and secrete a new tube. [4]
A number of sea anemone species are commensal with other organisms. Certain crabs and hermit crabs seek out sea anemones and place them on their shells for protection, and fish, shrimps and crabs live among the anemone's tentacles, gaining protection by being in close proximity to the stinging cells.
Urticina eques in a Channel Islands sea bottom rich in marine life. Also seen are a purple sea urchin, a chestnut cowrie, and many strawberry anemones. Urticina eques is dioecious. In California, female ripeness occurs in December as the sea temperature begins to fall.
It is one of the few sea urchin that can survive many hours out of water. [45] Sea urchins can be found in all climates, from warm seas to polar oceans. [40] The larvae of the polar sea urchin Sterechinus neumayeri have been found to use energy in metabolic processes twenty-five times more efficiently than do most other organisms. [46]
If the sea urchin comes into contact with the tentacles of the sea anemone, it may be unable to tear itself free, however, if it is swathed in seaweed fragments or concealed among the seaweed fronds, the sea anemone's tentacles may adhere to the algal material, enabling the sea urchin to make good its escape. [5]
These sheets of tissue develop into tentacles on the surface of the anemone. The tentacles of many species of anemones are found in multiples of six. Unlike other anemone the fish-eating anemone does not possess an acontia, which is thread-like tissue made up of stinging cells that function as a defense mechanism to protect against predators.
Urticina crassicornis, commonly known as the mottled anemone, the painted anemone or the Christmas anemone, is a large and common intertidal and subtidal species of sea anemone. Its habitat includes a large portion of the coastal areas of the northern hemisphere, mainly polar regions, and it lives a solitary life for up to 80 years. [ 1 ]