Class Coral polyps. Eight- and six-pointed corals. Characteristics, nutrition and structure. Characteristics and structure of coral polyps What are coral polyps

Representatives of the class Coral polyps are invertebrate organisms that inhabit the depths of the seas. Basically, colonial organisms, sometimes solitary, polypoid form.

general characteristics

Coral polyps belong to the type of intestinal animals, which includes the following classes: hydroid, scyphoid and coral polyps (the most large group). The latter are divided into subclasses: eight-beam and six-beam.

coral polyps

The first (eight-beam) includes colonial individuals with eight tentacles (red coral, sea pen, blue coral). Polyps of the second subclass (six-rayed) in most cases solitary, with six tentacles (anemones, black corals).

Today there are about 6,000 species coral polyps that inhabit salt water bodies in various climatic zones. Most are found in zones with a warm climate (water temperature fluctuations are about 18-22 degrees), they can be located at a considerable depth of the sea if they are provided with food - plankton.

The structure of coral polyps

The body shape of Coral polyps resembles a cylinder. Three balls are distinguished in the wall: ecto-, meso-, endoderm.

ectoderm forms a cover layer, often has a calcareous structure, which, after the death of the organism, forms a polyp forest.

mesoderm- This is a gel-like substance found in all cavities of the polyp. The internal space is divided into chambers with the help of partitions. The number of chambers is equal to the number of tentacles.

The upper pole is represented by a mouth opening, which is surrounded by brightly colored tentacles (therefore long time they were considered plants). At the lower end is the sole, which serves as an attachment to the substrate. The mouth communicates with the stomach cavity through a long tube (pharynx), which is presented as a wide flattened slit. At its ends are long cilia that are constantly moving. Thus, in the cavity of the polyp, water, which is necessary for the vital activity of Corals, continuously circulates. Oxygen and food enter here, and after metabolic processes, carbon dioxide and digestion products are removed.

They lead a motionless lifestyle, attaching to the substrate, branching like the branches of a plant. Each branch consists of small polyps that form a colony. Newly formed individuals are attached to the previous ones, so their growth is carried out, for a year the increase in growth is 1 cm. Massive growths of coral polyps form reefs.

For protection, coral polyps are equipped with special thread-like organs with stinging cells; when a dangerous agent approaches, they are thrown out of the mouth opening.

The division of coral polyps can be sexual and asexual (budding). When new individuals are formed, they swim freely in the water for some time, but soon they find a substrate, attach to it and begin development.

Subclass Six-pointed corals

Six-pointed corals have tentacles in the mouth area, the number of which is equal to or a multiple of six. Many have a calcareous skeletal structure, or organic.

Squads of six-pointed corals

- solitary skeletal polyps, brightly colored, with the help of a muscular sole, slowly move along the bottom of the sea. They are able to form a symbiosis with hermit crabs, which help to overcome long distances, in turn, sea anemones protect them with their stinging cells. Representatives: anemone telia, anemone metridium.

- These are single or colonial polyps, with a well-developed calcareous skeleton (consists of calcium carbonate). Single individuals live in deep seas, at the very bottom and reach 50 cm in diameter. Closer to land there are large colonies of Madrepore corals, stretching for a couple of meters and weighing several tons. Representatives: ceiloria, favia, brain coral. They are the basis for the formation of reefs.

- representatives of the detachment have a colonial structure. The internal skeleton is solid, allows it to grow up to 6 meters in height, it contains a specific protein - antipatin, which causes a black color. They are used to make jewelry, so there is an intensive extraction of them, which put this species to the brink of extinction.

Subclass Eight-pointed corals

Most individuals of the colonial structure, consist of small polyps (up to 1 cm). There are eight tentacles on the mouth opening. The internal skeleton is represented by deposits of calcareous structures in the mesoglea.

Squads of eight-pointed corals

- soft corals, exist due to symbiosis with photosynthetic organisms, through which they receive energy, some feed on plankton. They take part in the formation of reefs, are used as a habitat for fish.

- inhabit the depths of the seas, consist of a stem (primary zooid) and budding individuals that diverge to the sides, forming branches. They are attached to the bottom surface with a wide leg and lead a sedentary lifestyle.

- a horn skeleton is located inside, in some representatives it is painted red (used in the jewelry industry).

Nutrition of representatives of the class Coral polyps

Corals get their nutrients in two ways.

1. Individuals living at depth are able to independently capture plankton, microscopic crustaceans, fish larvae, and substances dissolved in water. For example, gorgonians have a branched structure and grow towards the current, which makes it easier to capture nutrient particles. For a normal existence, polyps also need not organic matter: calcium, magnesium, potassium.
2. Many corals live in symbiosis with plants and receive food in the process of photosynthesis (under the action of sunlight, oxygen and glucose are formed from carbon dioxide, which are partially transferred to the body of the polyp).

Corals are able to change their feeding paths depending on changes in the environment; with insufficient energy supply due to symbiosis, plankton consumption increases.

Coral polyps or marine - living creatures that may not move at all, and if they move, then very little. They live at the bottom of the sea large groups are rarely alone and do not have a backbone.

You can find more precise definition What are polyps, biologists say - these are some forms of aquatic animals that have stopped at a certain stage of development. And at the next stage, a jellyfish is already obtained. Among this class, you can count about 6 thousand species, among them there are even those that do not have a skeleton, which consists only of protein.

If we translate literally from Latin the name of coral polyps, then we get such a funny name - an animal - a flower. It is this name that indicates the shape of the polyps themselves. All of them really resemble a flower, they can be of different diameters, sometimes they reach a diameter of about 60 cm, and the height may well be a meter. Coral polyps can be used as aquarium decorations, and they are also used by jewelers to make jewelry.

Coral grows about one centimeter per year if they grow in comfortable conditions. They grow on great depth, because it is there that a large amount of plankton lives, they feed on it. And large polyps that live alone can eat small fish.

Polyps can reproduce in two ways: the first is the larva, which is obtained from the mating of jellyfish, it settles somewhere and begins to grow. The second is the division of polyps into parts, in other words, sterile reproduction. Jellyfish appear thanks to polyps.

There are certain types of polyps that cannot turn into a jellyfish. Such polyps create coral reefs, they have only a skeleton consisting of lime.

Since it was already mentioned earlier that some polyps do not have a skeleton, anemone belongs to them. She lives alone, can be of impressive size - about one and a half meters. They lead an exclusively sedentary lifestyle, while they can also coexist with some species of fish. Very large sea anemones can even feed on fish that have the average size. They may well move along the bottom due to the fact that they compress and unclench the sole, but very slowly.

In nature, there are not only polyps that do not turn into a jellyfish, since they do not have this stage, but there are also jellyfish that cannot become polyps.

Polyps are very important in the environment, they clean sea ​​water from organic particles. Also, coral limestone can be used for construction, but not in all countries. It is coral polyps that take part in the formation of reefs.

There are amazing forms of corals. Some of them resemble underwater flowers. Each "twig" of such a flower consists of many individual polyps.

   Class -
   Row - Alcionaria, Gorgonaria, Madreporaria, etc.

   Basic data:
DIMENSIONS
Diameter: individual polyps up to 2 cm, colonies reach an average of 3 m.

BREEDING
They reproduce asexually by fission and budding. Colonies also produce sperm and eggs. The fertilized eggs hatch into larvae.

LIFESTYLE
Habits: lead a sedentary lifestyle seabed; there are individuals and columns.
Food: living plankton. Madrepore corals feed on the waste products of algae that live in their body.

RELATED SPECIES
The class of coral polyps includes more than 6,500 species of stony corals, sea feathers, gorgonians, sea anemones and many other animals. Jellyfish are not their close relatives.

   Coral polyps are unique underwater architects. In shallow waters tropical seas they form whole fabulous forests and glades, which are perfect place for the existence of many marine animals.

FOOD

   Coral polyps are active at night. They feed on plankton and organic particles in the water.
   Corals catch their prey with paralyzing stinging cells, the burning fibers of which are studded with small hooks. Many coral polyps live in symbiosis with unicellular algae. Algae receive carbon dioxide and nitrogen and phosphorus compounds necessary for photosynthesis from the coral. Corals use both the main and by-products of photosynthesis - organic matter and oxygen. Between the owner and cohabitant there is a continuous exchange of phosphorus.

BREEDING

   A coral colony grows as a result of budding, that is, asexual reproduction, when a small offshoot appears on an old individual, which turns into a new young individual. Buds appear on tissues that connect individuals in a colony, or that grow on the sole of the parent polyp. During sexual reproduction in the first phase of the month after the full moon, corals release billions of eggs and sperm into the water. All polyps of the same species release their germ cells into the water at the same time. The fertilized eggs develop into small larvae that become part of the zooplankton.

LIFESTYLE

   Colonies of coral polyps are a large number of separate polyps firmly attached to each other, which together form twigs, horns or other complex forms. Individual polyps are shaped like a short cylinder with a hole at the upper end, surrounded by a rim of tentacles. Special tubules connect several layers of cells and transfer digested food to other members of the colony. Coral polyps can be divided into two groups. The first is formed by polyps that build a calcareous skeleton, they are called madreporous corals. The second group includes polyps with feathery tentacles, such as gorgonians, sea feathers and sea anemones. Coral polyps strengthen their massive skeleton with a special layer formed by the sole. Thanks to such a strong base, in case of danger, the polyp can instantly draw the body into the calcareous skeleton. Other types of corals are like large fans, they can bend and sway under the action of sea currents, because their skeleton is created by separate calcareous rods that are in a jelly-like substance.

HABITAT

   Most often, coral polyps are found in shallow warm seas. Usually the water temperature here does not fall below -16 C. For stony corals, the most optimum temperature is within 23 C. If the temperature changes significantly, the corals may die. Some types of coral polyps need to be reached Sun rays. Madrepore corals are found ideal conditions at a depth of up to 45 m, soft and mobile alcyonari are found up to a depth of 100 m. Madrepore corals do not settle near river mouths, because they do not survive in fresh, running water. "Hunting" coral polyps willingly settle in the area of ​​​​sea currents. Thin, but elastic gorgonians perfectly tolerate light waves of water (their columns are elastic and bend), while hard, but fragile stony corals break under the influence of water or waves.
  

DO YOU KNOW WHAT...

• Corals "fight" among themselves for territory. Coral polyps shoot burning fibers from their neighbors or grow in such a way that they block the light.
• In the Mediterranean in in large numbers mined noble coral. They make jewelry out of it.
• Red coral is colored in various shades of red - from light pink to dark red. The most expensive coral is the rare black coral.

  

TWO CORALS OF THE NORTH ATLANTIC

   Alcyonaria: it is a coral that lives alone. It looks like an anemone, so it is easy to confuse it with it. The animal reaches 25 mm in diameter, its transparent tentacles grow like a corolla around a slit-like mouth opening.
   Gorgonians: lives in Atlantic Ocean, in the waters, are warmed by the Gulf Stream. The colonies of this polyp form a horny, lime-impregnated skeleton.

PLACES OF ACCOMMODATION
Found in all tropical and subtropical seas, as well as in some areas temperate zone. Reefs form on the warmer eastern part of the continents.
PRESERVATION
Corals are very fragile animals, so they are often destroyed by the anchors of ships that drag along the bottom.

These are truly amazing inhabitants our planet is inhabited by the waters of the oceans. They chose the seabed as their "home". What are we talking about? About corals!

Many will say: how can animals be so similar to plants, and in general - are corals really animals? As it is not surprising, but - yes, corals are precisely animal organisms, albeit not similar to the usual representatives of the terrestrial fauna.

The correct name for these creatures is coral polyps, in total there are about 5,000 species of them in the world. The variety of shapes and colors of these animals is simply amazing, just look at these patterned plexuses, it's just amazingly beautiful!

But let's look at corals in terms of scientific approach, since these are animals, then they must eat, breathe, move, multiply ... let's try to find out how they do it.

The structure of these bottom organisms is quite primitive. The body of corals is a cylindrical formation, at the end of which there are numerous tentacles. AT scientific classification The class of Coral polyps is divided into two subclasses: Six-pointed corals and Eight-pointed corals.

This bushy coral is a colony of polyps.

Hiding among the tentacles of a coral polyp oral cavity. The digestive system in these animals is represented by the "mouth", pharynx and blind intestinal cavity. It is in the "intestine" of the polyp that there are special cilia, thanks to which the life process of the whole organism is carried out.

These very cilia create a constant flow of water in the cavity of the polyp, and with water the animal receives oxygen for breathing, nutrients (the smallest living organisms, small fish and plankton), and also throws waste products back into environment. As you can see: special bodies coral polyps do not have respiration, sense organs and excretory organs. But what about the ability to move?

Coral polyps can make movements, but not too actively, as far as the structure of the skeleton allows them. These animals can only slightly bend their body, as well as move their tentacles.

Sex cells in corals do not mature in separate organs, but directly in the body cavity. As you can see, the device of these animals is quite simple, however, this does not prevent them from leading a full life on the seabed.

Coral polyps (if we consider a separate organism) are tiny creatures. One polyp grows in length from a few millimeters to one to two centimeters.

But a colony of polyps is already a rather large formation, visible to our eyes, forming a kind of “bush” growing on the bottom soil. The only exception is, perhaps, only a representative of madrepore corals, their body reaches a diameter of up to half a meter.

The skeleton of corals is internal (formed by a special protein) and external (from above it is enveloped by calcium carbonate secreted from the body of the polyp).

If we talk about a colony of coral polyps, then there is a so-called hydroskeleton - this is the water contained in the body cavity of all the "inhabitants of the colony". Through the joint efforts of the cilia of all members of the colony, water constantly circulates through the "common body", thus supporting not only the vital activity, but also the shape of the coral polyps.

Most often, corals inhabit warm zones ocean waters, but there is also certain types for which the cold is not terrible. Such cold-resistant polyps include gersemia. For normal life, coral polyps need only salt water, if even the slightest desalination occurs in their habitat, this is already fatal for the polyp.

Most of all, these animals love to live in clear and clean water. The depth of dwelling is generally small. Corals prefer good light, which is scarce at great depths. But some species climb on great depth(for example, batipates lives at a level of 8000 meters from the surface of the water!).

Coral polyps grow very slowly, with an average rate of 1 to 3 centimeters per year. Hundreds and even thousands of years pass before reefs and even entire coral islands, known as atolls, form at the bottom of the sea. By the way, more recently, scientists were, whose age is 4000 years! This is a real long-liver of our planet, researchers have never met another similar organism.

To reproduce, coral polyps use two methods: vegetative and sexual. In the first case, a “daughter” buds from the parent individual, eventually turning into an independent organism. Sexual reproduction occurs in a certain season and only ... on a full moon. And there is no mysticism in this, but only physics clean water, after all, during the full moon, the strongest tides occur in the oceans, which means that the chances for the spread of germ cells are much greater.

Corals are valuable organisms, and not only because they are used to make expensive jewelry and decor items. Coral colonies form entire ecosystems in which many marine animals live and breed.

The most famous "coral giant" in the world is the formation off the coast of Australia, called the Great barrier reef, its length is 2500 kilometers!

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Class Coral polyps (Anthozoa)

This class includes colonial, rarely solitary coelenterates. The length of one coral polyp from a colony is several millimeters, and the diameter of single polyps (for example,actinium ) can reach 1.5 m. In coral polyps, the medusa stage is absent.

Like hydroid polyps, corals have a corolla of tentacles around the mouth opening. The intestinal cavity is divided by radial septa intocameras . As a rule, animals of this class leadpassive lifestyle . However, solitary coral polyps (such as sea anemones) can t crawl on the ground with the help of a fleshy sole.

All colonial coral polyps have a skeleton consisting in most cases of calcium carbonate, less often of a horn-like substance. Colonial coral polyps with a calcareous skeleton form coral reefsand coral islands. Solitary coral polyps have no rigid skeleton.

Colonial coral polyps feed on small planktonic animals, trapping them with tentacles with stinging cells. In addition, algae settle in the body of many colonial corals, from which the polyps receive nutrients. Anemones are predators: they prey on big booty- crustaceans and fish.

Coral polyps have separate sexes. Sex cells develop on the partitions of the intestinal cavity. The spermatozoa go outside and penetrate the females. Fertilization occurs in the intestinal cavity. After crushing the fertilized egg, a floating larva is formed. She leaves the mother's body, swims for a while, and then settles, attaches to the bottom and turns into a small polyp.

Coral polyps have asexual reproduction- by budding. Huge coral colonies are formed as a result of budding that does not reach the end: individual daughter, granddaughter polyps are connected together. Some sea anemones can divide longitudinally. About 6 thousand species of coral polyps are known. In northern and Far Eastern seas Russia has about 150 species.

The origin of the coelenterates. According to one hypothesis, coelenterates originated from unicellular animals as a result of non-disjunction of daughter cells after division. According to another, they appeared due to the repeated division of the nucleus in the cell, followed by the formation of partitions between the daughter nuclei. Representatives of most classes are already known in the Cambrian; at the end of the Paleozoic, there was a mass extinction of the ancient coelenterates. In total, about 20,000 extinct species of this type are known. Many of them, having a massive skeleton, took part in the formation of thick layers of limestone.

The value of coelenterates.Some non-skeletal sea anemones (sea ​​anemones ) serve good example symbiosis. They coexist withhermit crabs living on their shells. Cancer feeds on the remains of sea anemone prey, and in return transfers it from place to place - to more successful places for hunting. Another sea anemone symbiotes withclown fish. bright fish, immune to the poison of the tentacles, lures enemies, and the sea anemone grabs them and eats them. Something falls to the clown. Individual sea anemones live (in aquariums) up to 50-80 years.

Some colonial polyps (eg.stony corals ) surround themselves with a massive calcareous skeleton. When a polyp dies, its skeleton remains. Polyp colonies, growing over thousands of years, form coral reefs and entire islands. The largest of them - the Great Barrier Reef - stretches along eastern shores Australia at 2300 km; its width is from 2 to 150 km. Reefs in their places of distribution (in warm and salty waters with a temperature of 20-23 °C) are a serious obstacle to navigation.

Coral reefs are unique ecosystems in which a huge number of other animals find shelter: mollusks, worms, echinoderms, fish. AT glacial period coral reefs bordered many islands. Then the sea level began to rise, and the polyps average speed a centimeter a year built on their reefs. Gradually, the island itself was hidden under water, and in its place a shallow lagoon formed, surrounded by reefs. The wind brought the seeds of plants to them. Then animals appeared, and the island turned into a coral atoll.

Many fish feed on coral polypsand hide among the calcareous branched "forests" built by these animals. sea ​​turtles and some fish feed on jellyfish. In addition, the intestinal cavities themselves, being predators, affect marine animal communities by eating planktonic organisms, and large sea anemones and jellyfish also eat small fish.

The person uses some coelenterates. First of all, from the dead calcareous parts of coral reefs in some coastal countries, construction material, when roasted, lime is obtained. Some types of jellyfish are edible. Black and red coral used to make jewelry.

Some swimming jellyfish, sea anemonesand corals can inflict very severe burns fishermen, divers and swimmers. Coral reefs hinder navigation in some places.

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