Classification:

KINGDOM: Animal

PHYLUM: Cnidaria

CLASS: Anthozoa

ORDER: Actiniaria

The sea anemone is an invertebrate along with 95% of all the other creatures that inhabit the earth.  The name Cnidaria refers to the cnidae, or nematocysts, which all Cnidarians posses.  Cnidae are cells which provide the anemone a means of capturing prey and  in defending themselves with a painful sting.  Corals, jellyfish, and hydras are also included in this phylum.  In all, there are about 1,000 species of sea anemones in all the oceans.

Appearance:

Sea anemones look like beautiful flowers.  The shape of the anemones body and its bright color give it a plant like appearance.  The are typically blue, green, pink, red, or a combination of colors.  They have column-shaped bodies with the mouth at one end, and the pedal disk at the other end.  The pedal disk is a muscular organ for attachment to substrates.  The mouth is located on a corresponding structure, the oral disk.  The oral disk is lined with rows of tentacles.  Anemones have soft bodies and some even cover themselves with coatings of sand grains or mucus-like secretions, but most do not form parts that can be recognized as fossils.  Some anemones such as the giant sea anemone of Australia can attain a diameter of up to 1 meter.

Habitat:

Sea anemones are found on rocky shores and in coral reefs around the world.  Some species can even be found at very low depths.

Prey:

Feeds upon small sea animals and tiny fish.

Reproduction:

Most sea anemones reproduce sexually and asexually.  Asexual reproduction occurs in two ways.  By splitting longitudinally (Longitudinal fission ordividing in half), or by pedal laceration which occurs when bits of tissue pieces later regenerate an entire small anemone. They can also reproduce by budding.  When it buds, a young sea anemone grows out of the base of the parent's body.  It eventually breaks off and grows by itself.  Sexual reproduction occurs seasonally.  Gametes are released from the gonads located on the partial septa into the gastrovascular cavity.  They are released and fertilized externally.  Fertilized eggs develop into a free-swimming planula larvae.  It then settles onto a hard substrate and metamorphoses into an anemone.

Behavior:

Most actinarians are sessile which means that they live attached to rocks or other substrates and do not move.  They can move but only very slowly by contracting the pedal disk. Some anemones burrow into sand and a few are even able to swim a short distance by bending the column back and forth or by flapping their tentacles.

Anatomy:

The sea anemone has a tubular gullet that leads internally from the mouth to the large gastrovascular cavity.  Ciliated grooves called siphonoglyphs found along the edge of the gullet beat inward to provide a resperatory current of water in to gastrovascular cavity.  Cilia on the rest of the gullet wall beat outward in order to remove wastes and foreign particles from the gastrovascular cavity.  During feeding, the beat of the cilia along the gullet wall is reversed in order to aid in moving food particles into the gastrovascular cavity.  The gastrovascular cavity is divided into sections by tissue called septa.  Acontia is septal filament that is extended below the partial septa.  Acontia bears numerous nematocyst that act to subdue living prey taken into the gastrovascular cavity.  On the septa near the oral disc is the ostia.  Ostia are round openings that allow circulation of fluid between adjacent sections of the gastrovascular cavity.

Interesting Fact:

Most sea anemones survive in a symbiotic relation with  marine algae called zooxanthellae.  Zooxanthellae is an organism which performs photosynthesis.  The zooxanthellaes waste products are used by the anemone for food.  Zooxanthellae are generally light brown.  The loss of zooxanthellae is apparent by the whitening of the anemone.  The anemone will slowly grow smaller and smaller until it dies if it looses its zooxanthellae.

Bibliography

1.  Lytle, Charles F.  1996.  General Zoology: Laboratory Guide The McGraw-Hill

     Companies, Inc.  ISBN0-697-13669-8.

2. Sea Anemone

     http://www.encyclopedia.com/articles/11630.html

3. Barnes, Robert D.  1985.  The World Book Encyclopedia World Book, Inc. 

     ISBN 0-7166-0085-4.                  

.