The coelenterates fall into three main classes:
- hydrozoans, represented by hydras and caravels;
- cyphozoans, represented by jellyfish;
- antozoa, represented by actinias or sea anemones and corals.
They are hydrozoans with a polyp shaped body. They live in freshwater, preferably in cool, clean waters, attached at one end to a rock or aquatic vegetation.
They are green, brown or gray. Some hydras can get around with somersaults.
They are colonies formed mainly by several transparent polyps that as a whole, are floating on the water of the oceans. In the colony, different groups of polyps perform different functions. Some promote the digestion of food, some the reproduction, others the protection of the whole colony, for example.
Caravel, colonial organism. They live offshore and have long tentacles of up to 20 meters or more. The stinging substances it manufactures can cause serious burns to humans.
They have a jellyfish body. Its size varies greatly from one species to another. Some may be a few millimeters in diameter while others are more than two meters in diameter. Certain jellyfish of the genus Cyanea, which live in the Arctic Ocean, have tentacles up to 30 meters long.
THEsea anemones or sea anemones
They have body shaped polyps. They have a variety of colors and sizes, ranging from a few millimeters to a meter or more in diameter. They are found attached to a support: a rock, a piece of wood or carapaces of other animals.
O clown fish or host spends all the time near sea anemones. He hides from danger and sleeps amid the anemone's poisonous tentacles. Sometimes she even steals food from her protector's mouth, although she also brings food to a place where she can reach it. This small fish, unlike others, is safe from anemone stings.
Why clownfish do not suffer from the effects of anemone stinging cells is not yet well known. Some scientists believe that the mucus that covers the fish protects it from poison. However, only healthy clownfish are protected. The sick are killed by the anemone.
The clown fish or host is found in the Atlantic and Pacific oceans. It is small, agile and brightly colored. The female lays her eggs at the base of a sea anemone.
The corals are organized in colonies of small polyps that make an exoskeleton or external calcareous skeleton. As with caravels, in coral colonies there is a division of labor among its members, with some groups capturing food, others promoting reproduction, and so on.
The corals have the most varied colors, such as red, white, pink, orange or yellow. Therefore they are widely used in aquarium decoration and even in jewelry making. They generally live in waters with average annual temperatures between 20 and 25ºC and a depth of approximately 35 meters. However, some corals have been found living at great depths.
When they die, their skeletons remain intact and support other colony polyps, thus forming the coral reefs. In many cases, these reefs pose a danger to vessels, constituting true underwater traps.
Coral Reef Seen From Under the Sea
Coral reefs form a barrier for vessels that reach the coast.