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A giant green anemone found in one of the many pools
Small group of aggregating anemones open in pool of water
Group of open aggregating anemones in water Large mass of closed aggregating anemones on exposed rock Group of open and closed aggregating anemones Group of open and closed aggregating anemones with solataire anemones on right Large colony of aggregating anemones along with large mussel bed Open aggregating anemones Close up of aggregating anemones with bits of shell covering body Closed aggregating anemones covering upper part of exposed rock

Aggregating Anemone ( Anthopleura elegantissima )

Aggregating anemones are typically small in size in the adult form. They range from less than an inch in diameter to a little over an inch. They appear pale green when open but most often found closed up and covered with bits of shell and other objects. These anemones also form large colonies composed of hundreds of animals tightly packed together.
Solitary anemone with sand covering oral disk
Anemone in closed state during low tide Anemone in closed state during low tide Close up of body area of anemone Solitary anemones in closed state on exposed rock Open anemone Image of solitary anemone just under water Close up of anemone

Solitary Anemone (Anthopleura sola )

Solitary Anemones are the most common non-aggregating anemones. The colors range from bright green, to pale green and even grayish and yellow. When under water, the tentacles are exposed and visible. When the anemone is exposed to air or disturbed, they will close up and sometimes have lots of small bits of shell and other objects attached to the body. ( other names: Sunburst Anemone, Starburst Anemone )

Sea Anemones

Types of Anemones

There are three types of Sea Anemones that are found in the intertidal zone in Southern California. They are the Aggregating Anemone, Solitary and Giant Green Anemones. Aggregating Anemones are much smaller than the Solitaire Anemones and the Giant Green. Aggregating anemones are easily identified as they are much smaller than the other two species. They also live in large colonies with individuals tightly packed together. The Giant Green anemones usually live in deeper water and are rare in southern California tidepools. Solitary anemones can be differentiated from the Giant Green as the tips of the tentacles of the Solitary are pinkish in color. Solitary anemones also have darker lines on the Oral Disc where the Giant Green anemones do not.

Description - Sea Anemones are a very alien looking set of animals that live in the intertidal zone. Anemones have many tentacles that radiate out from the mouth area located at the top of the central body. The body is roughly cylindrical with the mouth ( oral disc ) at the top and a foot ( pedal disc ) at the bottom. The pedal disc is used by the animal to securely attach to the rock. Sea anemones can range from a deep green color to a light yellowish and grey color depending on location and species.

Feeding – Anemones use their tentacles to capture various prey items. Anemones will feed on just about any animal that wanders to close to the tentacles or happens to fall in. Anemones will feed on small fish, snails, limpets, crabs and other marine life. The tentacles of the Anemones are covered with specialized stinging cells called Nematocysts. The Nematocysts will shoot a very small barb connected to the cell by a tiny thread into the prey item. The barb has a type of venom the will help paralyze the prey and the sea anemone will slowly draw the prey item into its mouth.

These stinging cells however do not work very well on animals with hard shells or very thick skin like… humans. That is why touching the tentacles may feel sticky but they will not hurt you. Crabs, Snails and other animals may be captured by the anemone but will eventually escape as the Anemone cannot digest the hard shell and will regurgitate the animal intact.

Protection – Sea Anemones have several ways they can protect themselves from the natural elements. Sea anemones will close up tight when the sea water recedes during low tide. This helps prevent the sea anemones from drying out when exposed to air. Sea anemones when closed can frequently be seen with several small bits of shell fragments and rocks sticking to the outer body when closed up. Scientist think this helps reflect the sunlight and keep the animal cool when exposed to air and the hot sun. The stinging cells also help protect the animals from predators. The primary predators of sea anemones are nudibranchs, sea stars and some fish species.

Ecology – Sea anemones are found in the lower tide zone always close to water. They prefer to live in water as much as possible but will tolerate a periods of time exposed to air. They can be found in pools, cracks, depressions and other places where water will settle that provides moisture. Sea anemones are found in calmer areas with less wave exposure. A good supply of water is however needed to bring a constant supply of prey.

Sea anemones can move around if their current location is no longer suitable. It may take a while for them to move but they will eventually get there.

Sea Anemones have a very special adaptation that allows them to thrive in a very hostile environment. Sea Anemones have algae growing inside their bodies. These are single celled plants that make energy from the sun by photosynthesis. The relationship between these algae and the sea anemones is beneficial to both. The Sea Anemones get oxygen and the algae get protection and other essential nutrients from the Sea Anemone. This relationships is call a symbiotic relationship where both the algae and Sea Anemone benefit.

This alga is also what makes the Sea Anemones look green. The algae however need sunlight to live. Sea Anemones that live in covered areas or deeper underwater appear yellowish and grey in color as they have less algae in their bodies.

One of the ways Aggregating anemones reproduce is by cloning themselves. Each large colony is the result of a single animal that has cloned themselves over many generations. In some situations when a colony comes into contact with another colony, a very distinct line ( about an inch ) will separate the anemones from each other as the members of one colony will not coexist with another colony.

Sea anemones have specialized fighting tentacles that they use when defending their territory or location. These are called acrorhagi and similar to the feeding tentacles but have a whitish tip. These tentacles are extended from the top part of the sea anemone.
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