Class Coral polyps (Anthozoa). Corals and all the most interesting things about them Colonial coral polyps include

These are exclusively marine, mostly heat-loving organisms. There are both solitary and colonial forms (the latter more often). There is no jellyfish form in the development cycle.

Compared to hydroid polyps, they are more complex. An individual coral polyp of a colony resembles a hydra in appearance, but is usually located in the calyx of its exoskeleton. The complication of their organization is the presence of a pharynx, dividing the intestinal cavity into chambers using vertical partitions, which increases the surface area for secretion and absorption of food.

There is a separation of the muscular and epithelial parts of the epithelial-muscle cell and the formation of differentiated muscle tissue.

The nervous system is of a diffuse type, but with a greater concentration of nerve cells at the mouth opening than in Hydra.

Coral polyps reproduce both asexually and sexually. The gonads develop in the endoderm of the intestinal septa.

The fertilized egg begins to fragment. First, it divides in two, then each of the resulting cells, in turn, also divides, and so on. As a result, a large number of small cells arranged in one layer and looking like a small hollow ball. Following this, some of the cells are immersed inside, resulting in a two-layer embryo. The endoderm is subsequently formed from its inner layer, and the ectoderm of the future polyp is formed from the outer layer. The ectoderm is covered with numerous small cilia, with the help of which the embryo gains the ability to swim; from this moment it turns into a larva called planula. The planula is unable to feed or reproduce. It swims in the water column for some time, then sits on the bottom and attaches itself to it with its front end. Soon after this, a mouth opening breaks through at the posterior end (now upper) end of the planula and a corolla of tentacles is formed. This is how the first polyp appears. In colonial forms, this polyp soon buds on itself other polyps, which in turn follow, etc. a colony appears. Once the colony reaches a certain stage of development, the polyps that make it up begin to reproduce also sexually, forming eggs. This completes the cycle.

Among solitary soft coral polyps, widely known sea ​​anemones, which are called sea flowers for their varied colors.

Colonial forms are numerous and varied (spherical, tree-like, etc.). Their skeleton is made of calcium carbonate. Calcareous skeletons of colonial forms form reefs and oceanic islands - atolls. Organic red skeletonnoble coral used for making jewelry.

Control questions:

What structural features are characteristic of coelenterates (using the example of Hydra)?

How does hydra feed?

What types of reproduction does hydra have?

Which common features and are there differences between representatives of the classes Scyphoid and Coral polyps?

How do Scyphoids reproduce?

beauty underwater world, its splendor and diversity always amaze nature lovers who go to see sea ​​creatures. At the heart of this diversity are some very unusual inhabitants.

Introducing Interesting Facts about corals

Corals have the most extraordinary range of colors, which shimmer beautifully in the ocean depths.

In total, there are more than 6 thousand such underwater inhabitants in the world and this is one of the richest species of coelenterates.

Corals are quite picky

So, for their growth they need adequate conditions: sufficient salinity of water, transparency, warmth and a lot of food. That is why coral reefs live in the waters of the Pacific and Atlantic oceans.

It is interesting that in the World Ocean the area of ​​coral reefs totals about 27 million square meters. km.

The Great Barrier Reef is considered one of the greatest creations of these underwater growths. It extends near Australia.

Lime reserves thanks to coral reefs are almost inexhaustible

Some areas of such reefs are so large that they can rightfully be called coral islands.

The coral islands have own life and vegetation. You can even find cacti and tall shrubs here.

The local population uses corals to make jewelry.

The results are very beautiful and rainbow-colored products for the summer season.

Corals are also used as a building material, polishing metal surfaces and producing medicines.

If a person is damaged by the coral barrier, the skin will take a very long time to heal. Even suppuration may appear at the wound site, regardless of whether poisonous coral or not.

Corals have special cells designed to protect

They are called stinging insects and at the moment of danger they release poison.

The Hindus had a belief that only men should wear red corals, and only women should wear white corals. It was believed that these colors are a kind of symbolism of one and the other sex, and in the case of “wrong wear”, each of them acquired the character traits of the opposite. How true this is is unknown.

Today, few men wear coral products. Well, women allow themselves any color scheme and red as well. Apparently, it is precisely because of this that emancipation is flourishing in our country.

You will find other interesting facts about corals on the Internet.

There are more than 5000 different coral species. The length of the coral polyp does not exceed 1 cm, and in all other respects it is very similar to an anemone. In fact, sea anemones are coral polyps, but solitary and without a skeleton. Most coral species live in tropical seas. Some polyps live solitarily, but most species form large colonies. Some build a strong skeleton around themselves. It is from these skeletons that coral reefs gradually form. The skeleton of horn corals resembles a branched tree or deer horns. The skeleton of soft corals is like spongy rubber jelly. Corals- These are coelenterates. Like everyone else, they obtain food with hunting tentacles. But unlike other classes, coral polyps do not have a jellyfish stage in their life cycle; they spend their entire lives as polyps. In a coral colony, each polyp is connected to neighboring living tissue, most often in the area of ​​the sole. Thus, the colony acts as one giant super organism. Each polyp catches prey independently, but then the food is distributed among neighboring members of the colony. This is important because in some corals certain polyps cannot feed themselves, their function is to protect or support the colony by building exoskeleton.

In reef-building corals, each polyp forms under itself and on the sides of the body a cup-shaped skeleton made of calcium salts dissolved in water. If danger arises, such as an attack or starfish eating corals, they are drawn into a protective bowl. Later, when the danger has passed, the animal leans out.
Feeding polyps spread small tentacles and catch food particles brought by waves and currents. Hunting tentacles capture small animals and protozoa and direct food into the mouth, like their large relatives -. Many polyps come out to hunt only at night. It is at this time that marine plankton rises closer to the surface. Polyps with fluttering, shiny tentacles make coral reefs look like a sparkling, multi-colored carpet.
At favorable conditions, usually on the night of a full moon, all the corals in a certain area simultaneously release eggs and sperm into the water. Clouds of reproductive products float near the surface. Each egg is fertilized by a sperm and develops into a tiny larva that swims in the sea for some time. Later it sinks to the seabed, attaches itself to rocks and develops into a coral polyp equipped with a corolla of tentacles. If this single individual survives safely, after a few weeks it buds several new polyps - a small colony is formed. As the number of individuals increases, the colony grows.

Coral polyp resembles a miniature sea anemone. His body is entirely occupied by the digestive cavity. Folds of the inner layer of cells (mesentery), growing inside the cavity, increase the surface area for absorption of nutrients.
Some corals form bright, branched growths that are hard and leathery to the touch.
Reefs formed by corals have many cavities, caves and overhangs - perfect shelters for other creatures!
During the breeding season, corals release clouds of eggs and sperm into the seawater.

Groups of corals:
- Madrepore corals – with a stony skeleton, the main reef builders.
- Alcyonaria (soft corals)
- Horn corals (gorgonians) – sea fans
- Sea feathers

Coral polyps (lat. Anthozoa) are a class of marine invertebrates of the cnidarian type. Colonial and solitary benthic organisms. Many types of coral polyps have a calcareous skeleton and participate in reef formation. Along with them, this class includes many representatives whose skeleton consists of protein (gorgonians, black corals), as well as those completely devoid of a hard skeleton (anemones). There are about 6 thousand species. The name Anthozoa literally means an animal - a flower; on the one hand, it determines the zoological character of this group, and on the other, it indicates their appearance. They really look like flowers: multi-colored, with movable tentacles resembling petals, and many of them are quite impressive in size. Others are up to 60 cm in diameter and up to a meter high. Along with aquarium fish and plants, coral polyps are kept in aquariums. The skeletons of some species (coral) are used in jewelry.

Fig.1. Coral polyps (lat. Anthozoa)

Corals live in the sea; they are motionless and resemble plant branches in appearance. However, these are not plants: each coral branch is a cluster of tiny animals, coral polyps. Such clusters are called colonies. Each polyp forms a protective calcareous shell around itself. When a new polyp is born, it attaches to the previous one and begins to build a new shell - this is how the coral “grows”. Coral “growth” is about 1 cm per year in favorable conditions. Large concentrations of corals form so-called coral reefs. Coral polyps live in warm tropical seas, where the water temperature is not lower than 20 ° C, and at depths of no more than 20 meters, in conditions of abundant plankton, which they feed on. Usually during the day the polyps shrink, and at night they stretch out and straighten their tentacles, with the help of which they catch various small animals. Large single polyps are capable of catching relatively large animals: fish, shrimp. Some species of coral polyps live due to symbiosis with autotrophic protozoa (single-celled algae) that live in their mesoglea. There are muscle cells that form longitudinal and transverse muscles. Available nervous system, forming a dense plexus on the oral disc.

Corals are usually called only the skeleton of the colony, which remains after the death of many small polyps. Many coral polyps are reef builders. The skeleton can be external, formed by the ectoderm, or internal, formed in the mesoglea. As a rule, polyps occupy cup-shaped depressions on the coral, visible on its surface. The shape of these polyps is columnar, in most cases with a disc at the top, from which the corollas of the tentacles extend. The polyps are motionlessly attached to a skeleton common to the entire colony and are connected to each other by a living membrane covering it, and sometimes by tubes piercing the limestone.

The skeleton is secreted by the outer epithelium of the polyps, and mainly by their base (foot), so living individuals remain on the surface of the coral structure, and the whole thing continuously grows. The number of polyps involved in its formation also constantly increases through their asexual reproduction (budding). In many eight-rayed polyps, the skeleton is poorly developed and is replaced by a hydroskeleton, which is ensured by the filling of the gastric cavity with water. Corals also reproduce sexually, forming tiny free-swimming larvae, which ultimately settle to the bottom and give rise to new colonies. Polyps are usually dioecious. Spermatozoa enter the gastric cavity through ruptures in the gonad wall, and then out and penetrate through the mouth into the cavity of the female individual. Fertilized eggs develop for some time in the mesoglea of ​​the septa. In many coral polyps, development proceeds without metamorphosis and a larva is not formed.

In a series of experiments conducted on the corals of the Great Barrier Reef, a trigger mechanism was identified that triggers the death of corals. Their death begins with an increase in the organic content in water and sediment, and microbes are the mediator of these processes. An environment rich in organic matter provides a good basis for the rapid growth of microbes, as a result of which the oxygen content and pH of the environment decrease. This combination is lethal for corals. Accelerating sulfate reduction, which uses dead tissue as a substrate, only accelerates the death of corals.

They differ in the following features: they have large sizes; rarely solitary, more often colonial forms; live in warm tropical seas, the temperature is not lower than 20C 0, the depth is not great; Most species have a well-developed skeleton (horny or calcareous), the skeleton can be external, formed by the ectoderm, or internal, formed in the mesoglea; The gastric cavity is divided into chambers by partitions - septa. There is an ectodermal pharynx with flagellar grooves - siphonoglyphs, which ensure the flow of water into the gastric cavity; gonads are formed in the endoderm; there are muscle cells that form longitudinal and transverse muscles; the nervous system forms a dense plexus on the oral disc; radial symmetry is broken and a transition to biradial or bilateral symmetry is observed; the mouth is surrounded by either eight tentacles (eight-rayed corals), or a multiple of six tentacles (six-rayed corals). Reproduction is asexual and sexual. Development with metamorphosis. The larva is planula. There is no alternation of generations.

Coral polyps have a varied diet. Many feed on plankton or catch small animals using tentacles. Large single polyps - sea anemones are capable of catching large animals: fish, shrimp. Some species live through symbiosis with unicellular algae. Sea anemones are predators. Fish, crayfish, crabs are their desired prey. The anemones grab her with their tentacles, and now hundreds of poisonous “arrows” pierce her. A short convulsion - and now the sea anemone, having pulled its prey to its mouth with its tentacles, turns its throat out of its mouth. It covers the caught animal with it, then it, along with its throat, disappears inside the sea anemone. From living in aquariums, sea anemones “lost weight” greatly: they lost ten times their weight! But as soon as they were offered food again, they greedily began to swallow it and quickly “recovered.” After a few days it was hard to believe that the sea anemone had fasted for so long.

When sea anemones develop an appetite, they swallow everything indiscriminately, even inedible and dangerous objects. One sea anemone “out of hunger” swallowed a large shell. The sink stood across her “stomach” and divided it into two rugs, upper and lower. No food came from the mouth into the lower one. They thought the sea anemone would die. But she found a way out: at the sole of the sea anemone, at the very place where this “sea flower” sits on the stone, a new mouth opened its toothless mouth. Tentacles soon grew around it and the sea anemone became the happy owner of two mouths and two stomachs. Colonial polyps are “lifelong prisoners” of the colony they form. They are not allowed to separate from it and move independently. But sea anemones, squeezing and unclenching their soles, crawl along the bottom. Not quickly, but they crawl, they can climb onto a sink, onto a stone or other object lying at the bottom. Sea anemones breathe oxygen dissolved in water, pumping it through their mouth: water enters the sea anemone from the corners of the slit-like mouth, and back from the middle part of the slit. Sea anemones love water with fairly high salinity. In the Mediterranean Sea near Naples, where the salt content of the water is 3.7%, about 50 species of sea anemones live, in the Black Sea, with water salinity half as much, there are only 4 species, and in the Sea of ​​Azov (a very slightly salty sea) there is only 1 species.

Internal and external structure

Sea anemones have mainly large forms of single polyps, devoid of a skeleton. They are often brightly colored and are called sea anemones. They have the shape of a cylinder, with an average height of 4-5 cm and a thickness of 2-3 cm. They consist of a middle part, called a trunk (column), ending at the bottom with a leg, with which it is attached to underwater rocks, and an upper part, consisting of oral disc, or peristome, which has a mouth in the center in the form of an oblong slit. Around the mouth and along the edges of the trunk there are tentacles arranged in groups. Each group includes as many tentacles as there are spaces between the tentacles forming the inner circle, i.e. each gap is occupied by tentacles from the next group. The first and second circles have 6 tentacles each, the third - 12, the fourth - 24, the fifth - 48, i.e. the number successively doubles. The number of circles varies from one to six, eight, ten or more. The sea anemone has a wide variety of forms - tomato, flower, fern leaves.

Fig.2. Transverse sections through eight-ray and six-ray polyps

The gastric cavity is complex. The mouth leads into a pharynx, flattened in one direction, with a folded ectodermal lining. In Hexacorallia there are two siphonoglyphs in both corners of the pharyngeal cleft. Siphonoglyphs ensure the flow of water through the gastric cavity. The slit-like pharynx and the presence of two siphonoglyphs violate radial symmetry and therefore sea anemones have only two planes of symmetry. The pharynx leads into the gastric cavity, which is divided by radial partitions - septa.

Fig.3. Schemes of the structure of coral polyps

Septa are lateral folds of the endoderm, each fold correspondingly consisting of two layers of endoderm, between which there is mesoglea with muscle cells. The septa adhere to the pharynx with their free edge, but do not close below the pharynx, forming the stomach. The edges of the septa are thickened, corrugated, seated with stinging and digestive cells, forming mesenteric filaments. Their free ends are called acontia. The prey is digested under the influence of enzymes. Hexacorallia has many septa, at least twelve. The muscular ridges in the guiding chambers face outward and do not break the biradial symmetry determined by the shape of the pharynx and the two siphonoglyphs. Sea anemones lack a skeleton.

Corals as symbionts

Corals are a unique community of shallow-water marine organisms tropical zone of the World Ocean, represent a symbiosis of corals and unicellular algae. During the process of photosynthesis, unicellular algae release free oxygen, which is necessary for coral polyps for respiration, and the corals in return release carbon dioxide, which is very necessary for algae for photosynthesis. Such corals supply single-celled algae with various nutrients.

Coral reefs are highly productive communities that combine a stable photosynthetic system and a system capable of capturing, preserving and entraining life cycle nutrients from ocean water containing plankton and suspended particles. Sea anemones are in symbiosis with hermit crabs, mosaic crabs, and grooved angular crabs. Sea anemones with stinging properties protect crayfish from enemies. Hermit crabs serve sea anemones for movement. Sea anemones are placed on the surface of the shell, creating protection in the form of a cape that does not impede the movements of the crayfish. The sea anemone's mouth opening is located above the crayfish's mouth, and it freely captures part of its food. However, crayfish are not the only representatives of crustaceans with which sea anemones are associated. Similar phenomena are observed in other species. Of the sixty individuals of Actinolotus reticulata and Hepatus chiliensis caught on the coast of Chile, only four were without anemones. Each mosaic crayfish cell contains sea anemones. Sea anemones have friendly relations with amphiprion fish.

Clowns, swimming between the tentacles of sea anemones, set the water in motion, and this brings oxygen, helping the sea anemone to breathe. In addition, small food also comes to it with the flow of water. The symbiosis of giant sea anemones or sea anemones and small brightly colored ones is very interesting. clown fish. Sea anemone is a predator. Fish that find themselves close to the tentacles of sea anemones are affected by the poison of its stinging cells. And clowns swim among them completely calmly and feed on scraps of food that they collect from the tentacles of sea anemones. Apparently, the clown is protected from the effects of poison by the mucus covering its body. The sea anemone, in turn, “eats up” the remains of food that the clown gets, because, having grabbed the prey, it brings it to a safe place - that is, to the sea anemone. The poisonous tentacles of the sea anemone provide the clown with reliable shelter. Under her protection, he lays eggs at the sole of the sea anemone and sometimes even rubs against its tentacles.

Polyps play a huge role in cleansing sea ​​water from suspended organic particles. Coral limestone is used in construction in some countries. Certain types of coral are highly valued as material for various jewelry. That is why some corals are on the verge of destruction and currently require careful protection from poachers. Coral polyps are the main reef-building organisms.



Class Coral polyps (Anthozoa)

This class includes colonial, less often 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. Coral polyps do not have a jellyfish stage.

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 along the ground using 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 calcareous skeletons form coral reefsand coral islands. Single coral polyps do not have a rigid skeleton.

Colonial coral polyps feed on small planktonic animals, capturing them with tentacles containing stinging cells. In addition, algae settle in the body of many colonial corals, from which the polyps receive nutrients. Sea anemones are predators: they hunt large prey - crustaceans and fish.

Coral polyps are dioecious. Germ cells develop on the partitions of the intestinal cavity. The sperm come out and penetrate the females. Fertilization occurs in the intestinal cavity. After crushing the fertilized egg, a floating larva is formed. It leaves the mother's body, floats for some time, and then settles, attaches to the bottom and turns into a small polyp.

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

Origin of coelenterates. According to one hypothesis, coelenterates evolved from single-celled animals as a result of non-divergence of daughter cells after division. According to another, they appeared due to repeated division of the nucleus in the cell with the subsequent formation of partitions between the daughter nuclei. Representatives of most classes are known already in the Cambrian; at the end of the Paleozoic there was a mass extinction of 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 meaning of coelenterates.Some non-skeletal sea anemones (sea ​​anemones ) serve good example symbiosis. They coexist withhermit crabs , living on their shells. The cancer feeds on the remains of the sea anemone's prey, and in return transfers it from place to place - to places more favorable 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 goes to the clown too. Some sea anemones live (in aquariums) up to 50-80 years.

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

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

Many fish feed on coral polypsand hide among the limestone branched “forests” built by these animals. sea ​​turtles and some fish eat jellyfish. In addition, coelenterates themselves, being predators, influence marine animal communities by eating planktonic organisms, and large sea anemones and jellyfish also eat small fish.

Humans use some coelenterates. Primarily 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 corals used to make jewelry.

Some floating jellyfish, sea anemonesand corals can cause very serious damage with their stinging cells severe burns fishermen, divers and swimmers. Coral reefs impede shipping in some areas.

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