Sea Anemone
Classification
| Phylum: | Cnidaria |
| Class: | Anthozoa; subclass: Zoantharia |
| Order: | Actiniaria |
| Family: | Actiniidae, Stichodactylidae, Thalassianthidae |
What They Look Like
| SIZE:Diameter: | They range from 1.25cm (0.5in) to 1.5m (4ft 11in). |
 | Sea anemones, the "flower-like animal," are classified as cnidarians because they have stinging cells. |
| They have cylindrical (round) shaped bodies with one or more circular crowns of tentacles (usually occurring in multiples of six) around the mouth. |
| This single-opening cavity (called a coelenteron) performs all of their life functions: digestion, absorption, and gas exchange. |
| They also have either a pedal disk, used to attach itself to the substrate, or a bulb-like physa, which burrowing anemones use to anchor themselves in soft substrate. |
Geographic Range
| 1000 species |
| Live in all oceans |
| Larger, more colorful in warmer waters |
| Heteractis and Stichodactyla (specifically found on the Great Barrier Reef.) |
Natural History
Food Habits
| Though sea anemones could survive off the energy supplied by their symbiotic photosynthetic algae, they need sulfur, nitrogen, and other elements to grow and reproduce. |
| Ihe majority of sea anemones are passive predators. They use their specialized stinging cells (nematocysts) to immobilize any prey that blunders into them and then use their tentacles to draw them into their all-purpose mouth. |
| The stinging cells each have a coiled hollow filament, which is barbed and contains poison that causes the immobilization. |
Reproduction
Anemones reproduce both sexually and asexually. Asexually they practice either fission, splitting into two halves or base fragmentation, where the pieces grow into new individuals. Sexually, the separate sexes ejaculate either sperm or eggs, respectively, through their mouths. After a sperm and egg unite in the water and fertilization occurs, the egg becomes a planula, which eventually settles in a suitable environment and grows into a new anemone. Some research has shown that the eggs are fertilized within the female and later released, but this has yet to be conclusively proven.
Behavior
| The majority of anemones are predominantly sedentary (move very little).. |
| However, some glide very slowly on their pedal disk or move in a slow somersaulting fashion. Other species burrow deep into the sand or mud, leaving only their mouths exposed. Others float, with their mouths pointing downward, near the ocean surface. |
| Under extreme circumstances, anemones inflate and let the currents take them to a new location. |
Habitat
| Anemones live no deeper than about 50 m, generally in clear water because their symbiotic bacteria need light to perform photosynthesis. |
| Most live either some distance from reefs, on the sand-flats surrounding them, or actually on the reefs. |
| A select few can survive in muddy areas and they lack symbiotic bacteria. |
| Some hermit crabs deposit anemones on their shells for protection. The anemone benefits from the food dropped by the crabs. |
| Anemones also form a mutual protection relationship with clownfishes. The anemones protect the clownfishes from other larger fish and the clownfishes protect the anemones from butterflyfishes who would eat them. The clownfishes also use the anemone for reproduction with some anemones even containing a mating pair. |
| The fish also eat parasites on the anemones and fan them with their fins for greater circulation of water. They also form similar symbiotic relationships with other select fish and shrimp. |
Conservation/Biodiversity
| Sea anemones have few predators except the Grey Sea Slug. These species can decimate a colony of sea anemones in a very short amount of time. | ||||||||||
| A few anemones are listed as endangered:
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| The starlet sea anemone seems to be the most in danger. Others may be endangered or vulnerable, but are not so easily tracked. |
Economic Benefits for Humans
Positive
Researchers may use the sea anemone's venom to develop medications that prevent people from rejecting newly transplanted hearts, kidneys, and other organs.
Negative
Sea anemones have started to invade certain non-native habitats, like the Japanese striped sea anemone in the San Franciso Bay area. Some anemones also contain strong toxic substances which have serious effects on humans. The stinging anemone (Actinodendron plumosum), a blue-grey to light brown animal contains a strong toxin dangerous to humans.
Comments
The Magnificent Sea anemone (Heteractis magnifica) seen in the picture is a very colorful anemone. The base is usually red, purple, or pink contrasted by brown, green, blue, or purple tentacles. H. magnifica can grow up to one meter in diameter and the tentacles are the same width all the way to the tip. The clown fish within the tentacles may be a mating pair that have a symbiotic relationship with the anemone.
Image Source
| Reference: | Magnificent Sea Anemone (Heteractis Magnifica) with clown
fish.
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| Reference URL: |
http://www.cautiouscoral.com/images/anemone/96.jpg
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| Entry Author: | Erika Tilley | Union College | 2003 |