Only single coral polyps, and even then not all, are devoid of skeletal structures. On the contrary, colonial corals have a skeleton, most often consisting of carbonic lime, less often (in some eight-rayed Octocorallia corals) of a horn-like substance. In eight-rayed corals, the calcareous skeleton lies inside the mesoglea and in the simplest case consists of scattered microscopic calcareous needles (Fig. 112). The latter, like sponges, are formed inside special cells - scleroblasts. The noble coral has so many calcareous needles (spicules) that most of them merge into a dense mass, forming a solid skeleton. In six-rayed corals (Fig. 113), the calcareous skeleton is structured differently. In a young individual, first the plantar plate is secreted outward by ectoderm cells, and then a skeletal calyx, or theca, is formed around the body of the polyp. Further from the theca, skeletal septa (sclerosepta) grow into the body, protruding the wall of the polyp in front of them deep into its gastric cavity.
In colonies consisting of a huge number of individuals, the calyces of neighboring polyps often merge. So, at the connection. Octocorallia has an internal skeleton (located inside the mesoglea), in the subcl. Hexacorallia is external in origin, since it lies outside the ectoderm, representing a product of its vital activity.
Sclerosepta and real soft septa have a very definite number and location, which serve as an important systematic feature.
The eight-rayed corals Octocorallia (Fig. 111) have 8 septa dividing the gastric cavity into 8 peripheral chambers; two of these chambers, located opposite the narrow edges of the pharyngeal tube, are called guide chambers. On the septa, muscle ridges are located in a strictly defined order. As a result, two muscle ridges face the cavity of one of the directional chambers (conventionally called the ventral chamber). The muscular ridges do not protrude into the other guiding chamber (dorsal).
In six-rayed corals, the arrangement of septa is more complex (Fig. 111). The number of partitions arranged in pairs is a multiple of six, but there are at least 12 of them. Partitions do not all appear at once. First, six pairs of first-order septa are formed, with which the gastric cavity is divided into 12 chambers. Chambers lying between two partitions of one pair are called internal, while those located between partitions of different pairs are called intermediate. Further partitions appear in pairs, forming within the intermediate chambers.
Today, 5,000 species of corals are known. They resemble something like a tree, bush, carpet, ball, etc. They are popular due to the fact that they are very similar to precious stones. But most people don't even know, Is it an animal or a plant? We will answer this question in this article.
Is coral an animal or plant?
It is very difficult to understand with the naked eye what kind of organisms these 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 if you touch it. You've probably heard about So, they consist of millions of dead organisms, which after death harden like stone. If we look at it in more detail, a coral is a huge number of tiny organisms that together form a polyp. The structure of a 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, polyps of madrepore coral can reach 40-50 cm in diameter. Individual individuals are connected to each other through a coenosarc. As a result, a single organism is formed. All individuals obtain food together. The larger ones catch particles, the smaller 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 oldest coral reefs were created 23 million years ago. This suggests that the polyps appeared a very long time ago. As noted a little above, for the most part reefs present a large number of dead individuals. The exception is the top layer, which has formed recently.
Coral shapes and sizes
We can talk endlessly 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 and size. The smallest colonies are no more than a few centimeters in length, and the giants of the genus can reach 5-6 meters. As for the form, that's a separate conversation.
Some colonies can be very simple and consist of a twig or hook. Others are distinguished by their complexity. For example, the shape of a shrub or colony that resembles that of a tree is not uncommon. One can endlessly wonder how such things form something so beautiful and complex. There are representatives that grow not upward, but in breadth. Such colonies resemble mushrooms or small carpets. You're probably wondering what an animal or plant eats? Of course, in most cases they capture microorganisms, which may include both (plankton).
and habitat
Coloring may vary. But most often you can see brown and red colonies. Orange ones are somewhat less common. 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 very different 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 species are heat-loving. 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 shallow depths of up to 50 meters in places with the greatest illumination. It is extremely important for corals that they are constantly in 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 shape of the polyp, which resembles a shell, where moisture is retained.
A few more features
You've probably noticed that even the simplest coral can come in a wide variety of shapes and colors. Is it an animal or a plant? The answer to this question was voiced at the beginning of the article. But it is worth noting that if you do not touch the polyp, it is difficult to understand whether it is alive or not. However, by touching you can feel the skeleton of the animal. It is interesting that polyps always settle on a hard surface, since silt is not suitable for them. Large colonies can often be observed on long-sunk 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 classified as 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 because 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. Photos of the most interesting colonies can be found in this article.
Conclusion
Despite their simplicity, polyps surprise with their beauty, which is why many people are attracted to 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 catch entire colonies and make jewelry out of them. And they grow very slowly, about 1-3 centimeters per year. By the way, the growth process largely depends on the light and oxygen saturation of the water. It is for this simple reason that this issue comes up more and more often at meetings of researchers and conservationists. Over the course of tens of thousands of years, entire reef islands are formed, which are destroyed by humans 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 unite into entire colonies and ultimately build reef islands.
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 antlers. 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 up the 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. When danger arises, such as an attack or a starfish eating the corals, they are pulled into a protective cup. 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.
Under favorable conditions, usually at night during 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 are a class of marine invertebrate animals belonging to the phylum Coelenterata. These are colonial or, less commonly, solitary polyps that live in the seas. Currently, two subclasses are distinguished: eight-rayed and six-rayed coral polyps. The first group includes colonial organisms with 8 feathery tentacles (red coral, sea pen, organ). Polyps of the second group, mostly solitary, have a number of tentacles that is a multiple of six (anemones, madrepore corals). In total, approximately six thousand species of coral polyps are known, distributed in seas with high salinity in different climatic zones. Most coral polyps live in warm tropical seas with a water temperature of at least 20 degrees, at a depth of up to 20 m, provided there is an abundance of food - plankton.
The most primitive firms were found in strata dating back to the Cambrian period. Since the beginning of the Mesozoic era, subclasses of eight-rayed and six-rayed coral polyps have appeared on Earth.
Hydroid coral polyps differ from other representatives of the class in their more complex structure, the presence of a pharyngeal tube located inside the body and ending in the oral opening, the division of the body by radial partitions into separate cavities and a more perfect structure of the body as a whole. The vast majority of coral polyps form colonies; representatives of rare species are solitary.
These organisms have a typical cylindrical body shape. At the posterior end of the body there is a flat, round surface, the so-called “sole,” with which the polyps attach to objects under water. At the front edge there is a mouth opening with one or several rows of tentacles around the circumference. The mouth opening opens into a wide pharyngeal tube - a kind of stomach. The structure of the stomach wall is three-layered, similar in structure to the wall of the animal’s body. Undigested food remains are removed into the external environment through the mouth. The gastric cavity is multi-chambered due to its division into parts by radial septa. During the day, the polyps compress their tentacles, and at night they spread out and catch prey - various small plankton animals. Single polyps of large sizes can also catch larger animals - mollusks and fish.
Some types of coral polyps have stinging organs in the form of threads that perform a protective function, which, in case of danger, are thrown out through the mouth or through holes in the wall of the polyp's body. In the structure of the body wall of a coral polyp, three layers are distinguished - ectoderm, mesoderm and endoderm. The ectoderm covers the outside of the entire body of the individual and is the inner lining of the pharyngeal tube. The ectoderm consists of three layers: epithelial, nervous and muscular. Many representatives of this group of animals have a calcareous skeleton of ectodermal origin, which gives rise to horny and calcareous deposits that form the polypnyak. Mesoderm is a gelatinous substance that fills the cavities of coral polyps and includes spindle- or stellate-shaped cells and fibers. Calcareous bodies may also be present in the mesoderm, which sometimes join together to form a dense calcareous mass. The endoderm is divided into the same three layers as the ectoderm, but the structure of the ectoderm and endoderm layers is different. These organisms do not have special sense organs.
Reproduction of coral polyps occurs both asexually and sexually. Asexual reproduction occurs by budding. The development of germ cells occurs in the endoderm of the mesentery. Young organisms leave their mother at the planula stage, floating in the water column for a certain time, and then attaching to the bottom during transformation into an adult.
Extensive colonies of coral polyps are formed when budding does not reach completion. Corals in the seas are motionless and outwardly look like plant branches. But each coral branch is nothing more than accumulations of small animals - coral polyps. These clusters are called colonies. The coral “grows” with the birth of young polyps. If environmental conditions are favorable, coral growth is about 1 cm per year. When colonies of coral polyps grow in the tropics, barrier reefs and atolls (coral islands) are formed. The vast majority of coral polyps in reefs are six-rayed corals. Due to their calcareous skeleton, they are widely used as a building material. The Mediterranean Sea is home to red and black eight-rayed corals, the skeletons of which are highly prized as jewelry.
Coral polyps are a class of marine invertebrate animals belonging to the phylum Coelenterata. These are colonial or, less commonly, solitary polyps that live in the seas. Currently, two subclasses are distinguished: eight-rayed and six-rayed coral polyps. The first group includes colonial organisms with 8 feathery tentacles (red coral, sea pen, organ). Polyps of the second group, mostly solitary, have a number of tentacles that is a multiple of six (anemones, madrepore corals). In total, approximately six thousand species of coral polyps are known, distributed in seas with high salinity in different climatic zones. Most coral polyps live in warm tropical seas with a water temperature of at least 20 degrees, at a depth of up to 20 m, provided there is an abundance of food - plankton.
The most primitive firms of coral polyps were found in strata dating back to the Cambrian period. Since the beginning of the Mesozoic era, subclasses of eight-rayed and six-rayed coral polyps have appeared on Earth.
Hydroid coral polyps differ from other representatives of the class in their more complex structure, the presence of a pharyngeal tube located inside the body and ending in the oral opening, the division of the body by radial partitions into separate cavities and a more perfect structure of the body as a whole. The vast majority of coral polyps form colonies; representatives of rare species are solitary.
These organisms have a typical cylindrical body shape. At the posterior end of the body there is a flat, round surface, the so-called “sole,” with which the polyps attach to objects under water. At the front edge there is a mouth opening with one or several rows of tentacles around the circumference. The mouth opening opens into a wide pharyngeal tube - a kind of stomach. The structure of the stomach wall is three-layered, similar in structure to the wall of the animal’s body. Undigested food remains are removed into the external environment through the mouth. The gastric cavity is multi-chambered due to its division into parts by radial septa. During the day, the polyps compress their tentacles, and at night they spread out and catch prey - various small plankton animals. Single polyps of large sizes can also catch larger animals - mollusks and fish.
Some types of coral polyps have stinging organs in the form of threads that perform a protective function, which, in case of danger, are thrown out through the mouth or through holes in the wall of the polyp's body. In the structure of the body wall of a coral polyp there are three layers - ectoderm y, mesoderm y and endoderm y. Ectoderm a covers the outside of the entire body of the individual and is the inner lining of the pharyngeal tube. Ectoderm A consists of three layers: epithelial, nervous and muscular. Many representatives of this group of animals have a calcareous skeleton of ectodermal origin, which gives rise to horny and calcareous deposits that form the polypnyak. Mesoderm A is a gelatinous substance that fills the cavities of coral polyps and includes spindle- or stellate-shaped cells and fibers. Calcareous bodies may also be present in the mesoderm, which sometimes join together to form a dense calcareous mass. Endoderm A divided into the same three layers as the ectoderm A , but the structure of the ectoderm layers s and endoderm differently. These organisms do not have special sense organs.
Reproduction of coral polyps occurs both asexually and sexually. Asexual reproduction occurs by budding. The development of germ cells occurs in the endoderm of the mesentery. Young organisms leave their mother at the planula stage, floating in the water column for a certain time, and then attaching to the bottom during transformation into an adult.
Extensive colonies of coral polyps are formed when budding does not reach completion. Corals in the seas are motionless and outwardly look like plant branches. But each coral branch is nothing more than accumulations of small animals - coral polyps. These clusters are called colonies. The coral “grows” with the birth of young polyps. If environmental conditions are favorable, coral growth is about 1 cm per year. When colonies of coral polyps grow in the tropics, barrier reefs and atolls (coral islands) are formed. The vast majority of coral polyps in reefs are six-rayed corals. Due to their calcareous skeleton, they are widely used as a building material. The Mediterranean Sea is home to red and black eight-rayed corals, the skeletons of which are highly prized as jewelry.At first glance at corals, it is difficult to understand what kind of organisms they are or whether they are organisms at all. In fact, in their natural environment, corals resemble trees or shrubs, and when pulled out of the water they look like precious stones, because it’s not for nothing that jewelry is made from them. In fact, corals are animals, or rather colonies of tiny organisms - coral polyps. There are almost 5,000 species of coral polyps in the world, of which about 3,500 are actually called “corals.” Some representatives of coral polyps, for example, sea anemones, are not traditionally called corals, although they are closely related to “true” corals.
Red acabaria coral (Acabaria rubra).
The coral polyps themselves are structured in a rather uniform and primitive manner. Their bodies have an elongated cylindrical shape, at one end of which there is a corolla of tentacles. Thus, coral polyps are characterized by radial symmetry. Depending on the number of tentacles, two subclasses of Coral polyps are distinguished - Eight-rayed and Six-rayed corals. In representatives of these subclasses, the number of tentacles is always a multiple (but not necessarily equal) of 8 and 6.
The eight-rayed gray coral (Anthelia glauca) is one of the common inhabitants of aquariums.
Hidden between the tentacles is a mouth opening that leads into the pharynx and blind intestinal cavity. This cavity is divided by longitudinal cords (septa) into several chambers. The walls of the septa and pharynx have cilia that continuously move and create a constant flow of water through the body of the polyp. Coral polyps extract oxygen and nutrients from the water and secrete metabolic products there. Thus, corals do not have respiratory organs, excretion, or feelings. Their germ cells mature directly in the body cavity. Thanks to the muscle fibers in the body walls, coral polyps can move, but these movements are limited. Polyps can only slightly bend their body and shorten it, as well as protrude or hide tentacles.
The surface of the coral is formed by closely packed coral polyps.
The size of polyps is tiny - from a few millimeters to a couple of centimeters, so the size of corals is usually measured not by the size of an individual polyp, but by the size of the colony as a whole. As an exception, single madrepore corals are also found; their polyps can have a diameter of up to 50 cm. Individual polyps are connected to each other using a common base - the coenosarca, in addition, the cavities of their bodies are connected by holes and common connective tissue. Ultimately, it turns out that all members of the colony are connected into a single organism, jointly obtain food and redistribute nutrients among themselves. In most corals, colony members have the same structure and size, but there are some that have a “separation of responsibilities.” In this case, some polyps (autozooids) have large tentacles and catch food particles, while the rest (siphonozoids) drive water through the colony with their cilia and participate in reproduction.
This bushy coral is actually an entire colony of coral polyps.
All corals have a skeleton. In some species, the internal skeleton is of organic origin; it is formed by a protein (horny) substance concentrated in the connective tissue. In other species the skeleton is mineral and external. In this case, the bodies of the coral polyps secrete calcium carbonate (lime), which envelops them. In addition, in colonies there is a so-called hydroskeleton. The hydroskeleton is water, which is contained in the body cavities of all members of the colony: the cilia pump water into the body of the polyp under slight pressure, so it turns out that the water creates internal pressure and maintains the shape of the colony.
Coral dendronephthium polyps against the background of their own trunk. The trunk is supported by a hydroskeleton, that is, the liquid that fills it; additional strength is given to it by calcareous needles, which are visible inside the translucent substance.
The variety of sizes, shapes and colors of corals knows no bounds. The smallest colonies can be several centimeters in length, and the largest reach a height of 5-6 m! The shape of corals can be from very simple, resembling a single twig or curved hook (scourge shape) to complex, reminiscent of a tree, fan or candelabra.
Spiral ceripates (Cirrhipathes spiralis) is a deep-sea coral with a unique shape. Its colony resembles a thin twig, twisting into a spiral at the end.
Some colonies grow not up but out, resembling mushrooms, funnels, and flattened carpets.
A bizarre carpet formed by Acropora cerealis coral.
Finally, there are also spherical corals; their shape can be perfectly round or irregularly wavy.
And this “globe” is the surface of the plate coral (Platygyra lamellina).
Most often, corals are brown, white, red, less common are yellow, green, black, and pink. The rarest colors in corals are the blue-violet spectrum. But red acabaria corals come in two colors - deep red and bright yellow.
Coral polyps Palythoa toxica are one of the few species that have blue and purple colors in their color.
The vast majority of corals are thermophilic and are found only in tropical and subtropical waters; only a few species have penetrated far to the north and live in the polar seas (for example, Gersemia). In addition, all corals live exclusively in salty waters and cannot tolerate even slight desalination. Therefore, these animals cannot be found in the shallows near river deltas and in seas with low salinity, and vice versa, in highly saline, clean and transparent waters, corals thrive.
White Sea Gersemia (Gersemia fruticosa).
Most species prefer to live at shallow depths with good lighting (up to 50 m). This is due to the fact that corals often live in symbiosis with microscopic algae - zooxanthellae, which require light for photosynthesis. Among the corals, there are also those that have mastered the tidal zone of the coast. Although drying out is usually fatal to coral polyps, some madrepore coral colonies have learned to conserve water during low tide. Such colonies have a funnel-shaped shape, with the tentacles of all polyps directed inside the funnel; during low tide, water remains in this bowl and the corals do not stop their activity. Interestingly, colonies of the same corals, living a little deeper, do not have this shape.
In the heliopora heliopora (Diploastrea heliopora), individual polyps adhere very tightly to each other, forming a solid surface.
About 20% of coral species live at great depths, one of the deepest species is the curved bathypates, which can be found at depths of over 8000 m! Colonies of coral polyps usually appear on a hard substrate; these animals do not like muddy soils. Corals can also colonize artificial supports (the remains of sunken ships, underwater supports), but only those that have been in the water for a long time, since fresh paint is detrimental to polyps.
In the brain coral (lamella platygyra), individuals are so closely connected to each other that they even have common mouth openings.
Colonial corals lead a sessile lifestyle; few species of large single polyps can crawl slowly along the bottom (as sea anemones do). Despite their general primitiveness, corals exhibit complex biological rhythms. Most often, corals are active at night, at which time they stick out their tentacles and catch food particles from the water. At dawn, coral polyps shrink and remain dormant until dark. At the same time, some species can be active during the day or around the clock with certain circadian rhythms.
Gorgonian corals have a bushy shape.
Coral colonies grow very slowly. The growth rate largely depends on light, water temperature, oxygen saturation, the type of coral polyps and averages 1-3 cm per year, at best 10 cm. Corals with a hard calcareous skeleton, growing over several hundred and thousands of years, form reefs and even entire islands - coral atolls.
And in this type of gorgonian, branching occurs in one plane, so its colonies look like a fan.
Coral polyps are predators that feed on small animals. Cilia, driving water through the intestinal cavity, filter suspended organic particles, plankton and even... the smallest fish from the water. In some species, the tentacles are reduced, and food particles stick to the sticky mucus secreted by the polyps. At the same time, many species live in close collaboration with zooxanthellae. Microscopic algae find a hospitable home in the body of the polyp and protection from their own enemies, assimilate carbon dioxide (a product of the polyp's respiration), which is vital for photosynthesis, and the polyps, in turn, assimilate the organic substances that zooxanthellae synthesize and the oxygen released by them. Such cooperation goes beyond ordinary friendship, because corals without zooxanthellae gradually die. In nature, there is a natural death of zooxanthelids in corals as a result of excessive or insufficient light - the so-called coral bleaching. After partial bleaching, corals can recover, but after complete bleaching, they die within a few months.
The rich green color of the common galaxea (Galaxea fascicularis) is due to the presence of microscopic algae in its tentacles.
Corals can reproduce sexually and vegetatively. Vegetative propagation comes down to fragmentation and budding of a daughter individual from the parent polyp. In solitary madrepore corals, a “plate” is formed on the stem-leg, which falls off and attaches to the ground - this is a new organism. Meanwhile, the next individual continues to grow on the remaining stem.
Blistered plerogyra (Plerogyra sinuosa) is sometimes called “grape coral” for its thick, soft tentacles that look like berries.
Sexual reproduction is confined to a strictly defined time of year and even... night. Most corals are hermaphrodites, that is, they have both male and female gonads; only 30% of species are dioecious. Sperm and eggs are usually released on the night of the full moon, since during this period the highest tides are observed, which means that the likelihood that the reproductive cells will be carried away by the current is higher. In some species, sperm and eggs are released into the water and fertilization occurs in the external environment; in others, fertilization occurs in the cavity of the polyp itself and the already formed larva, the planula, emerges. Coral planulae are mobile, they can be carried over long distances by currents and ensure the colonization of new islands by corals. It is interesting that in those species that live in symbiosis with zooxanthellae, part of the algae is transferred from the parent colony to the larvae, so the planulae travel with the baggage of “friends” necessary for life.
All this diversity of the underwater landscape is formed exclusively by corals.
Corals have complex relationships with each other and other organisms. Some corals can coexist with each other; for example, soft eight-rayed corals, zoantharia and sea anemones often settle on gorgonians.
The red fan gorgonian (Leptogorgia ruberrima) is supported by a colony of its closest relative, the yellow gorgonian (Leptogorgia viminalis).
At the same time, different types of corals compete with each other and, when the edges of the colonies touch, they can infect rivals either with stinging cells or with special chemicals. The affected enemy's part of the colony that was attacked dies off. Parrotfish, triggerfish, and starfish feed on corals. But corals are also home to many species of living creatures - from the smallest invertebrates to sharks, and coral atolls provide shelter for birds, land crabs, and mammals.
A school of fish circles around a support inhabited by corals. In the foreground is an alcyonaria soft coral.
The importance of corals in nature is difficult to overestimate; these animals are landscape-forming; thanks to their activity, entire ecosystems with unique living conditions arise that cannot be reproduced simply on the underwater slopes of continents. The most famous formation is the Great Barrier Reef off the coast of Australia - a grandiose formation 2500 km long! For a long time, people have mined red or noble coral, the hard skeleton of which was used to make jewelry and inlay. Second in importance after red is black coral. Both species have become rare due to predatory fishing and their hunting is now prohibited in many places.
Red or noble coral (Corallium rubrum). The white “fluff” is the opened tentacles of the polyps.