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Cnidarians-jellyfish, sea anemones, corals and hydrozoans
There are four main types of cnidarians: jellyfish, sea anemones, corals and hydrozoans. Here you can gain information on all four types. Note: Jellyfish and hydrozoans are discussed under Part II
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Home of a clownfish
Clownfish have a mucus coating around their bodies that makes them immune to the sea anemone's sting. |
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The Celestial Sea Anemones
This beautiful underwater animal has always been known as the flower of the sea. In fact, in Greek, anemone means "wild flower." This is a common misconception. The sea anemone, in fact, is a meat-eating animal. They eat crabs, worms, and fish by using their hollow tentacles to stuff the food into their wide mouth. Their mouths are located in the center of the top end, surrounded by tentacles. Sea anemones have a tube-shaped body; one end is the mouth and tentacles, the other one is connected to a solid object. This could be the sea floor, a rock, or even a crab's shell! The tentacles of the anemone are covered in stinging cells for stinging prey, just like its relative, the jellyfish. Some fish, like the clownfish, are immune to the stings of anemones from a thick mucous coat covering themselves. When an anemone feels it is being threatened, it curls up into a tight ball, using its muscular body to retract extremely fast into its body cavity.
The sea anemone reproduces asexually by slowly pulling itself into two halves, often resulting in large groups of identical anemones.
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~Provided by the Microchip
Corals - takin' it to the reef
Like other cnidarians, corals are meat-eating animals that are non-mobile. They feed on small fish and plankton by reaching out small tentacles. Corals live in groups, and each individual of the group is called a polyp. Only the outer layer of a coral is made up of living polyps. The inside of a coral's structure is made of a hard calcium carbonate skeleton, which protects the polyps. When the polyps die, the skeleton remains, leaving a foundation for more polyps in the years to come.
Corals have a mutual relationship with algae. The algae provides food for the coral, and the coral provides protection and access to light for the algae. Because corals and algae need accessability to light, corals are found in shallow waters in sub-tropical areas. When coral skeletons build up so that they carry thousands of polyps, they are called a reef. There are three types of reefs. Fringing reefs grow seaward and project directly from the land mass. Barrier reefs are platforms that are seperated from a land mass by a strip of water. Atolls are reefs that grow near volcanoes that have broken the surface of the ocean.
Corals are said to have risen in the early Ordovician period (490 to 443 million years ago, according to the fossil record. Corals, along with sea anemones, are believed to be the most primitive cnidarians. Scientists' only proof of this is from the skeletons of coral found in fossils, as other cnidarians are soft-bodied, and therefore decay completely after death.
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The giant green sea anemone
Some species of sea anomones can grow to a diameter of three feet |
Coral communities
Coral reefs grow near the surface of the ocean, and provide a community for many different sea creatures. |
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