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coral structures

CORAL REEFS ARE THE MAIN ECOLOGISTS OF THE PLANET

There are over 5000 different coral species. The length of the coral polyp does not exceed 1 cm, but in all other respects it is very similar to the sea anemone. In fact, sea anemones are coral polyps, but solitary and without a skeleton. Most coral species live in tropical seas. Some polyps live alone, but most of species form large colonies. Some build a solid skeleton around themselves. It is from these skeletons that coral reefs are gradually formed. The skeleton of horn corals resembles a branching tree or deer antlers. The skeleton of soft corals is like a spongy rubber jelly. corals- these are intestinal. Like everyone else, they get food with tentacles. But unlike other classes, coral polyps do not have a jellyfish stage in their life cycle, they live all their lives in the form of polyps. In a coral colony, each polyp is associated with adjacent living tissue, most commonly in the sole area. Thus, the colony acts as one giant super organism. Each polyp catches prey on its own, 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 up the outer skeleton.

coral groups:
- Stony corals - with a stony skeleton, the main reef-formers.
- Alcyonaria (soft corals)
- Horn corals (gorgonians) - sea fans
- sea feathers

To date, about 5,000 species of corals are known. They resemble something like a tree, bush, carpet, ball, etc. Popularity is due to the fact that they are very similar to precious stones. But most people don't even know if it's an animal or a plant? We will answer this question in this article.

Coral is an animal or a plant

With the naked eye it is very difficult to understand what kind of organisms they are. This is due to several reasons. But it’s worth saying right away that coral is an animal, not a plant. They have a skeleton that can only be felt by touching it. You have probably heard of So, they are made up of millions of dead organisms, which, after death, harden like a stone. If you understand in more detail, then the coral is a huge number of tiny organisms, which together form the structure of the polyp is quite simple. It consists of a cylindrical body with tentacles. Between the latter there is a mouth opening.

Coral sizes and something else

Polyps are quite tiny, their size usually does not exceed a few centimeters. As for the colony that these creatures form, that is a completely different matter. For example, stony coral polyps can reach 40-50 cm in diameter. Separate individuals are interconnected by means of a cenosark. As a result, a single organism is formed. All individuals forage for food together. Larger particles catch particles, small ones participate in reproduction. So we have already figured out what corals are. Is it an animal or a plant? You already know the answer to this question. It is worth paying attention to the fact that the most ancient coral reefs were created 23 million years ago. This suggests that polyps appeared a very long time ago. As noted above, for the most part, reefs are a large number of dead individuals. The exception is the upper layer, which was formed recently.

Coral shapes and sizes

You can endlessly talk about the fact that there are a wide variety of colors of polyps. The same applies to their forms. If for the most part corals have the same shape, although there are exceptions, then they form the most impressionable and diverse colonies. This applies not only to shape, but also to color, as well as size. The smallest colonies are no more than a few centimeters long, and the giants of the genus can reach 5-6 meters. As for the form, this is a separate conversation.

Some colonies can be very simple and can be a twig or a hook. Others differ in their complexity. For example, the shape of a shrub or colony that resembles the shape of a tree is not uncommon. One can endlessly wonder how these form something so beautiful and complex. There are representatives that do not grow up, but in breadth. Such colonies resemble mushrooms or small carpets. Are you wondering what an animal or plant eats? Of course, in most cases they catch microorganisms, among which there may be both those and others (plankton).

and habitat

Coloring may be different. But most often you can see brown and red colonies. Somewhat less common are orange. It is even more difficult to find a green, pink or black colony. After all, not every scuba diver has seen blue-violet or bright yellow corals. They are considered very rare and do not live everywhere. As you can see, coral can be of various colors. It's an animal or a plant, you already know, so let's talk about where the colonies live.

The main habitat of corals is tropical and subtropical waters. The fact is that most of the species are thermophilic. But gersemia, one of the subspecies, lives far in the North. It is noteworthy that all polyps do not survive in fresh water, so absolutely all individuals live in a salty environment. Colonies settle at a shallow depth of up to 50 meters in places with the highest illumination. For corals, it is extremely important that they are constantly in the water, otherwise inevitable death occurs, but some individuals have learned to retain moisture for some time, for example, at low tide. The essence lies in the special form of the polyp, which resembles a shell, where moisture is stored.

A few more features

You must have noticed that the various shapes and colors can be even the simplest coral. Is it an animal or a plant? The answer to this question was given at the beginning of the article. But it is worth noting that if you do not touch the polyp, then it is difficult to understand whether it is alive or not. However, by touch, you can feel the skeleton of the animal. Interestingly, polyps always settle on a hard surface, since silt is not suitable for them. Large colonies can often be observed on long-wrecked ships.

The lifestyle of many species is sedentary. However, some constantly move along the bottom in search of food. By the way, corals can be safely attributed to predators. They go hunting at night. They stick out their tentacles and catch plankton and other organisms in the water. By the way, they do not search during the day due to the fact that the tentacles are very sensitive to ultraviolet radiation, such radiation can burn them. We have already answered your question about whether corals are animals or plants. You can find photos of the most interesting colonies in this article.

Conclusion

Despite their simplicity, polyps surprise with their beauty, which attracts many corals. The sea, especially if it is salty, can always show you the most interesting settlements of these animals. Today, it is very common to deliberately capture entire colonies and make ornaments out of them. And they grow very slowly, about 1-3 centimeters per year. By the way, the growth process largely depends on the illumination and saturation of water with oxygen. It is for this simple reason that this issue comes up more and more often at meetings of researchers and conservationists. For tens of thousands of years, entire reef islands are formed, which are destroyed by man in one day. Well, that's all that can be said about what corals are. Animal or plant? Of course, an animal, because these organisms can grow and combine into entire colonies and eventually build reef islands.

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 largest 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 of 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 for a 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 organs. filiform, 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 they are intensively mined, which has put this species on 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 normal existence, polyps also need inorganic substances: calcium, magnesium, potassium.
2. Many corals live in symbiosis with plants and obtain food through photosynthesis (using sunlight from carbon dioxide oxygen and glucose are formed, which partially pass into the body of the polyp).

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

Lifestyle

Most coral polyps inhabit warm tropical seas, where the water temperature does not drop below +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 able to catch relatively large animals: fish, shrimp. Some species of coral polyps live due to symbiosis with autotrophic protozoa (unicellular algae) that live in their mesoglea.

Structure

Coral polyps have 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, left after the death of many small polyps. Many coral polyps are reef builders. The skeleton may 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 disk at the top, from which the tentacles rims extend. The polyps are immovably fixed on a skeleton common to the entire colony and are interconnected by a living membrane covering it, and sometimes by tubes penetrating limestone.

The skeleton is secreted by the outer epithelium of polyps, and mainly by their base (sole), so living individuals remain on the surface of the coral structure, and all of it grows continuously. The number of polyps involved in its formation is also constantly increasing through their asexual reproduction (