If colonies of hydroids and gorgonians look like bizarre bushes and trees, then large coral polyps sea anemones(Actiniaria) resemble fantastic flowers. In many languages they are called sea anemones (see color table 9).
The order of sea anemones includes solitary, only occasionally colonial, animals leading an active lifestyle. Only a few deep-sea species are immovably attached to the substrate. Sea anemones have a cylindrical body shape with a flattened upper (oral disc) and lower end (solar). But in some sea anemones, mainly those that lead a burrowing lifestyle, a sole may not form.
The number of gastric septa in most sea anemones is at least six pairs or a multiple of six. The formation of new pairs of septa almost always occurs in the intermediate gastric chambers. However, there are deviations from this arrangement of partitions in which the number of partitions turns out to be equal to eight or a multiple of eight or ten. Typically, such deviations are especially characteristic of the most primitive sea anemones. It is known that in the process of individual development, all sea anemones go through the stage of four-ray symmetry, which possibly indicates the relationship of sea anemones with eight-armed coral polyps. The greatest similarity to modern eight-rayed corals is in from the genus Edwardsia. These sea anemones lead a burrowing lifestyle, living in the silty sandy soils of coastal shallow waters. Their body, on the surface of which eight longitudinal ridges are visible, has an elongated worm-like shape. The depressions between them correspond to the eight gastric septa. In addition to the eight complete septa, older specimens of Edwardsia develop four more, but incomplete, septa in the upper part of the body. Rolls of longitudinal muscle cords lie on the ventral sides of the septa in these sea anemones, as in the eight-rayed corals. Eight complete and eight incomplete septa are also formed in another archaic sea anemone, Gonactinia. The most well known European species gonactinia G. prolifera looks like a small, 2-3 mm long and 1-2 mm wide, transparent column with a soft pink or red color. The oral disc of the sea anemone is surrounded by sixteen delicate tentacles arranged in two rows. Its pharynx is so short that with its mouth open, eight main radial septa are easily visible in its gastric cavity. Gonactinia are attached with their soles to the substrate, most often to mollusk shells, and sometimes even to the trunks of hydroid polyps.
The number of partitions, a multiple of ten, is observed in representatives of the family Myniadidae, very peculiar sea anemones that have switched to a free-swimming lifestyle. They are supported in the water by a special air chamber, similar to the pneumatophore of a siphonophore, called a pneumocystis. It is formed as a result of strong invagination of the sole. At the same time, the edges of the sole come closer and close above the center of the disc recess. Therefore, sea anemone swims at the surface of the water with its mouth down. Like many other swimming coelenterates, Myniadidae are blue. In other sea anemones, the number of partitions, as already mentioned, is equal to six pairs or a multiple of six.
The free edges of the gastric septa have mesenteric filaments rich in glandular and stinging cells. Some anemones also form special filaments - aconcia, on which stinging capsules are especially numerous. To protect against attack, these threads are thrown out by sea anemones through the mouth or through special openings in the walls of the body or tentacles. The oral disk of sea anemones is surrounded by tentacles. Depending on the number of tentacles, they are arranged in one or two or even more concentric rows. In each circle, the tentacles are the same size and shape, but the tentacles lying in different circles are often quite different from each other. As a rule, the tentacles correspond to the spaces between the gastraligal septa. Usually the tentacles have a simple conical shape, but sometimes significant deviations from it are observed. In some species, swellings are formed at the ends of the tentacles due to the fact that numerous batteries of stinging capsules develop there. Some tropical shallow-water anemones develop branching or feathery tentacles. One or two pairs are formed at their ends, serving as an additional means for quickly emptying the body cavity.
The mouth opening of higher sea anemones has an oval or slit-like shape. The pharynx is strongly compressed laterally and has two siphonoglyphs. Only in the described primitive species there is only one poorly developed siphonoglyph or it is absent altogether. The beating of the cilia of the siphonoglyph creates two currents of water: one directed inside the gastric cavity and bringing oxygen (in some sea anemones and food particles), and the other moving in the opposite direction and carrying out carbon dioxide and excretory products.
The muscular system of sea anemones reaches a high level of development for coelenterate animals. The ectodermal system consists of longitudinal fibers lying in the tentacles and radial fibers around the mouth opening. The endodermal system consists of the circular muscles of the tentacles, oral disc, pharynx, body wall and leg disc. Longitudinal muscle ridges lie on the gastric septa.
The nervous system of sea anemones consists of an ectodermal network of nerve cells present in all parts of the body and a poorly developed endodermal network covering only the gastric septa. Especially many nerve cells are concentrated at the bases of the tentacles and on the oral disc. However, this does not lead to the formation of a perioral nerve ring, since the nerve cells are located here very loosely. Another cluster of nerve cells is located near the sole. It is interesting to note that different parts of the body appear to be particularly sensitive to certain stimuli. The sole, for example, is sensitive to mechanical irritations and does not perceive chemical ones. The oral disc, on the contrary, is very sensitive to chemical irritations and almost does not respond to mechanical ones. Perhaps only the walls of the body and tentacles react to mechanical, chemical and electrical stimulation, but the tentacles turn out to be much more sensitive to them than the walls of the body.
The sea anemone's usual reaction to irritation is to contract its body. At the same time, the oral disc and tentacles are retracted, and the walls of the body, compressed by a special muscle ring, close above them. Sea anemones that lead a burrowing lifestyle, like the Edwardsia described above, quickly burrow into the ground. When exposed to a stimulus for a long time, sea anemones tend to crawl as far away from it as possible.
Sea anemones do not form a skeleton, although the ectoderm of some species secretes a chitinoid cuticle that covers the lateral surface of the body and the sole. Perhaps only in deep-sea sea anemones from the family Galatheanthemidae, which lead a stationary, attached lifestyle, the strong cuticular sheath, which encloses the long worm-like body of the sea anemone, takes on the character of a protective skeleton, similar to the ectodermal skeleton of most hydroid polyps. Dark brown protective covers galatepeanthemide rise to a height of 2-3 to 150 mm. Above their mouth, about 1 cm in diameter, protrudes the upper part of the sea anemone’s body with a crown of numerous thin tentacles. Galateanthemids are one of the deepest-sea coelenterates. They were first discovered several years ago, when a period of systematic exploration of the maximum depths of the ocean began. These sea anemones most often live on the bottom and slopes of deep ocean basins - the Kuril-Kamchatka, Philippine, Japanese and others - at a depth of 6-10 thousand m. Their way of life has not yet been completely studied.
The body of sea anemones is sometimes very strong, although they lack a skeleton. The fact is that the mesoglea of sea anemones usually reaches significant development and often acquires the density of cartilage due to the appearance of a dense fibrous connective substance in it.
Sea anemones reproduce both asexually and sexually. However, asexual reproduction plays a much smaller role in them. Cases of budding in Actiniaria are generally very rare. More often, one individual is divided into 2 or even 3-6 unequal parts. Transverse division is noted only in primitive The greatest similarity to modern eight-rayed corals is in Gonactinia. In G. prolifera, for example, it proceeds as follows: at a certain height, a corolla of tentacles first grows from the body walls, then the upper part is laced and separated from the lower. At the top, the sole is restored, and at the bottom, an oral disc and pharynx are formed, as well as a second circle of tentacles. Second division gonactinium sometimes it starts before the first one ends.
Longitudinal division is more common in sea anemones. In this case, the oral slit is first divided into two, and then the entire oral disc undergoes the same division, and then the body of the sea anemone is also dismembered. Longitudinal division turns out to be a very long process. From the moment it begins until the complete separation of newly formed sea anemones, several months may pass. Occasionally, longitudinal division of sea anemones is observed, proceeding in the opposite direction - from the sole to the oral disc. In these cases, division proceeds very quickly and is completed in 2-3 hours (Fig. 178).
In addition to the described methods of asexual reproduction, sea anemones have developed another very unique method - the so-called laceration, in which several small individuals are formed at once. During laceration, a small section of it is separated from the sole of an adult sea anemone, containing the remains of the gastric septa. This area then gives rise to new sea anemones (Fig. 178). Although fission by laceration has been known since 1744, the complex process leading to the formation of young sea anemones has not yet been studied.
The ability of sea anemones to regenerate is very high, although it cannot be compared with that of freshwater hydras.
The main method of reproduction of sea anemones is the sexual process. The germ cells of sea anemones are of endodermal origin and mature in the mesogleal layer of the gastric septa. Sea anemones are usually dioecious, although cases of hermaphroditism occur. In these cases, male reproductive cells are formed before female ones (so-called protandric hermaphroditism). Fertilization can be either external or internal. In the latter case, young sea anemones reach the gastric cavity of the mother's body at the planula stage or the stage of formation of tentacles and gastric septa.
Reproduction of sea anemones that live in the cold waters of northern and southern latitudes usually begins in the spring and ends by summer. On the contrary, in tropical waters, sea anemones begin to reproduce in midsummer. Floating planula larvae stay in the plankton for 7-8 days and during this time they are carried by currents over considerable distances.
Sea anemones inhabit almost all the seas of the globe, but, like other coral polyps, they are especially numerous and diverse in warm waters. Towards the cold subpolar regions, the number of sea anemone species decreases rapidly. According to their lifestyle, sea anemones can be divided into benthic and pelagic. Myniadidae are an exclusively pelagic group. Bottom sea anemones have a very wide range of vertical distribution, occurring from the surf to the maximum depths of the ocean. But the vast majority of sea anemone species have adapted to living at shallow depths in coastal shallow waters. These are typical components of rocky fauna, forming dense settlements, moreover, often represented by a single species.
The distribution of shallow sea anemones largely depends on seawater temperature and salinity. In cold subpolar regions, the distribution of sea anemones is more or less circumpolar. Some cold-water sea anemones are found in both the Arctic and Antarctic, i.e. they form so-called bipolar habitats. In the tropical zone there are circumtropical species, but they are much less common than circumpolar ones. This is explained by the fact that tropical shallow areas are usually separated from each other by vast expanses of the ocean with its great depths. The large sea anemone Stoichactis has a typical circumtropical distribution. Some species of sea anemones, however, are insensitive to changes in water temperature. Such sea anemones are usually more widespread. Actinia equina, a common species in our northern seas, is found, for example, in the Atlantic Ocean as far as the Gulf of Guinea. As a rule, abyssal sea anemone species also have extensive ranges. Narrow localized ranges, however, are characteristic of ultra-abyssal anemone species that live at depths greater than 6000 m. Certain species of the genus Galatheanthemum, for example, apparently live in certain deep-sea depressions of the Pacific Ocean.
Although sea anemones are typical marine animals, many of them tolerate significant desalination of water. Several species of anemones are found in Kiel Bay and Ostsee, four species have penetrated into the Black Sea. In the Azov and Baltic seas, sea anemones are no longer found. It is curious that even in the relict Lake Mogilny on the island of Kildin, a crushed form of Metridium dianthus, which is very common in the northern seas, was found living there.
Burrowing sea anemones, such as Edwardsia or Haloclava, bury themselves more or less vertically in silt or silted sand and, when active, only protrude the upper end of their body with a crown of a few tentacles from the burrow. They prefer not to leave their burrow, but if necessary, they can crawl to a new place using wave-like contractions of the worm-like body. Having found suitable soil, the sea anemone stops moving and quickly fills its gastric cavity with water. She then releases some of the water and closes her mouth tightly. By this, she avoids the accidental loss of water remaining in the gastric cavity during instillation. When buried, the rear end of the body bends downward, towards the ground, and rhythmic waves of contractions of the annular muscles begin to run through the body. In this case, the water remaining in the cavity is constantly pumped from the anterior section to the posterior section and vice versa. With the help of peristaltic contractions, the body of the sea anemone is pushed deeper and deeper into the ground. After about an hour of hard work, the animal completely disappears into its new hole.
Most anemones have soles and lead a sessile lifestyle. But if necessary, they can also slowly move along the substrate. Typically, the forward movement of sea anemones is carried out using a fleshy sole. Part of it is then separated from the substrate, moved forward in the direction of movement, and is fixed there again. After this, the other part of the sole is separated from the substrate and pulled up. In particular, this is how Actinia equina, a widespread and very common species in our northern seas, moves. In the aquarium, A. equina was observed moving from the walls of the aquarium to nearby stones. The edge of the sole, separated from the glass wall, was strongly stretched and tilted towards the stones. Then the anemone hung with its tentacles down between the wall of the aquarium and the stone, to which the edge of the sole was already attached. After some time, its other edge separated and was pulled towards the stone. On the oral disc of this sea anemone there are 192 tentacles arranged in 6 rows. These sea anemones, brightly colored red or green, are very beautiful, especially in full bloom with a crown of delicately colored, slightly transparent tentacles. In the northern seas the predominant color of these sea anemones is green, and in the southern seas it is red. A. equina, due to its amazing undemanding nature, is one of the favorite objects for observation in aquarium conditions. Interestingly, live sea anemones can even be sent by mail, wet or wrapped in wet seaweed.
Sea anemones of other species move along the ground in a different way. For example, Aiptasia carnea completely separates its sole from the substrate and falls on its side. In this position lying on the ground, this sea anemone begins to move with its rear end forward with the help of peristaltic rhythmic contractions of the body in exactly the same way as burrowing sea anemones move. A. carnea always chooses night time for its travels.
Small sea anemones, like Gonactinia prolifera, can even swim, rhythmically throwing their tentacles back.
Most shallow-water sea anemones avoid daylight and crawl from sunlit areas to shaded rock crevices. If an anemone placed in an aquarium is suddenly illuminated with a bright light, it quickly contracts. Most shallow water anemones are therefore in a passive state during the day. They spread their tentacles at night or at dusk. However, littoral species of sea anemones are either indifferent to light, or even strive towards it, crawling to illuminated places or turning their oral disc towards the light. They are in a passive state at night.
Littoral species, which are indifferent to light, develop a different daily rhythm of life activity associated with tidal changes in water levels. A. equina, for example, spreads its tentacles with the tide and contracts at low tide. The daily rhythm of this sea anemone turns out to be so stable that after placing it in the aquarium it persists for several more days. Well-fed sea anemones can remain in a contracted state for a long time. On the contrary, hunger and low water temperature force sea anemones to remain in an active state for more than a day.
The nutrition of sea anemones has been studied relatively well. In some anemones, the main role in feeding is played by the grasping movements of the tentacles, in others - by the ciliated movement of ciliated cells scattered in the ectoderm. The former feed on various small living organisms, the latter on organic particles suspended in sea water. There are two main types of cilia movement. In primitive sea anemones, for example in Gonactinia, whose ciliated cells evenly cover the entire body, organic particles falling on the body are enveloped in mucus and are driven by the beating of the cilia from the bottom up, towards the oral disc, and then into the mouth. The beating of the cilia goes in the same direction on the tentacles. If the food bolus gets on the tentacle, then here too it is driven towards its upper end. The tentacle tilts towards the mouth, and the food is picked up by a stream directed towards the pharynx. Particles unsuitable for food are captured by the flow created by the cilia of the tentacles and, like food particles, move to the upper end of the tentacle. However, this tentacle no longer leans toward the mouth, but in the opposite direction. From the end of the tentacle, these particles are washed away by the flow of water.
In more highly developed sea anemones, cilia are formed only on the oral disc and tentacles. In particular, we find such a ciliary apparatus in Metridium dianthus, or sea carnation, one of the most beautiful sea anemones found in our waters (color table 9). On its long columnar body, numerous, over a thousand, thread-like tentacles are located in separate groups. The color of M. dianthus is extremely varied - from pure white to dark red. The movement of cilia on the tentacles and oral disc of these sea anemones is always directed towards the apex of the tentacles. All particles that fall on the oral disc or tentacles therefore move in the same direction. The tentacle, after the food bolus reaches its apex, bends towards the mouth. Then the lump is picked up by the cilia lining the pharynx and moves into the gastric cavity. Particles unsuitable for food also move to the upper ends of the tentacles, from where they are washed off with water or discarded.
Sea anemones, which grab food with their tentacles, feed on various living organisms, as well as pieces of meat left after the meal of some other predator. Numerous experiments have been carried out to give a good idea of the mechanism of grasping the prey and transporting it to the gastric cavity. Usually, hungry sea anemones sit completely calm, with their tentacles widely spaced. But the slightest changes occurring in the water are enough for the tentacles to begin to produce oscillatory “searching” movements. When an anemone smells food, not only part or all of the tentacles are extended towards it, but often the entire body of the anemone bends towards the food. Having caught the victim, the tentacles of the sea anemone contract and bend towards the mouth. It is very interesting to note that the pulling of the tentacles towards the mouth often occurs as a reflex, even regardless of whether the victim is grabbed or not. If large prey is captured, for example a small fish, then all the tentacles of the predator are directed towards it, and they all take part in transporting the victim to the mouth. Small prey is introduced into the pharynx using a current of water caused by the beating of ciliated cells in the ectoderm of the pharynx, larger prey is introduced using peristaltic contractions of the pharyngeal tube. In sea anemones with short tentacles, the pharynx turns slightly outward and is pulled towards the food, which is held above the oral disc by the tentacles, which are unable to bend down to the mouth opening. This is how he eats, in particular, bighorn sea anemone- Urticina crassicornis, found from the Mediterranean Sea to the North and Norwegian Seas. Numerous (up to 160) short and thick tentacles of this sea anemone surround its low and thick body. The coloration of U. crassicornis is extremely varied, and it is unlikely that two identically colored specimens of this sea anemone can be found at once.
U. crassicornis is also quite remarkable in that its method of reproduction depends on climatic conditions: in warmer waters this sea anemone spawns eggs, and in cold waters (for example, off the coast of Spitsbergen) it becomes viviparous.
Some sea anemones immediately sense the difference between food and unfit for food particles and never grab them. Others, especially in a state of hunger, grab any objects - stones, empty shells, filter paper, etc. After satiation, the previously indiscriminate anemones no longer introduce objects into their throats that are unsuitable for food. If you soak filter paper with meat extract, then at first the sea anemone readily grabs it. But over time, the sea anemone ceases to be too trusting. She will be able to fall for deception only after a certain period of time, when she feels hungry.
When this experiment is repeated several times, the sea anemone completely stops reacting to paper soaked in meat extract.
Species of sea anemones that feed on organic particles suspended in sea water have a poorly developed stinging apparatus of the tentacles. These sea anemones usually form long acontia, which perfectly protect them from attack. On the contrary, in predatory species of sea anemones, the stinging batteries of tentacles become very numerous. The volley of ejected stinging threads not only kills small organisms, but often causes severe burns in larger animals and even humans. Toilet sponge catchers are often severely burned by sea anemones. After a burn, the skin of the hands begins to turn red, itching and burning in the damaged area are accompanied by headache and chills. After some time, the sore spots on the skin die and deep ulcers form.
Many species of sea anemones are commensals of other animals or enter into peaceful symbiosis with them. These relationships of sea anemones to other animals have been discussed in detail previously.
Animal life: in 6 volumes. - M.: Enlightenment. Edited by professors N.A. Gladkov, A.V. Mikheev. 1970 .
Sea anemones are unusual in beauty and quite mysterious in their way of life. But where do sea anemones live? What is their appearance? Now we'll find out...
Scientists have long argued about what type of animal these creatures belong to, because they have something in common with both corals and jellyfish, and in appearance sea anemones generally look like underwater plants.
Modern classification classifies them specifically as coral polyps; moreover, these living organisms are among the largest representatives of corals.
Another name for sea anemones is sea anemones; the animals received this name precisely because of their resemblance to flowers.
The structure of the sea anemone is a body consisting of a corolla of tentacles and a cylindrical leg. At the base of the leg there are muscles (longitudinal and circular). The end of the leg may have a so-called sole.
Anemones are bottom-dwelling plants, so they need to gain a foothold on the surface of the ground; they do this with the help of various devices.
Some representatives of this type of coral secrete a special mucus, which tends to harden over time and thus firmly anchors the animal’s body to the substrate. Other sea anemones have such a large and strong leg that they are able to bury it in the ground and in this way securely attach themselves to the underwater soil.
But among sea anemones there are also exceptions that do not live on the bottom of the sea, but freely float in the water column. They are also called floats. In the sole of such species there is a special bubble that prevents the animal from sinking to the bottom and constantly maintains it in a floating state.
The upper part of the sea anemone's leg has a mouth opening, represented by a disk surrounded by many tentacles, which are arranged in rows.
These same tentacles are equipped with stinging cells that can shoot a thin thread containing a poisonous secretion. If you look at the sea anemone's body, you will notice pronounced radial symmetry.
As for the various sensory organs inherent in most living organisms, sea anemones in this sense can be called one of the most primitive.
The nervous system of these animals consists of sensory cells located at the base of the tentacles, around the oral disc, and also on the sole.
The main distinguishing feature of these sea creatures is undoubtedly their color. It is not for nothing that they are called sea flowers, because their colors contain the brightest tones: pink, orange, red, white, brown, green, yellow and others. In some species, you can find a whole rainbow palette on the body, since the body has one color, and the tentacles are painted in a contrasting shade.
The size of sea anemones is also surprising: the smallest representatives of this group of animals can have a millimeter height, and there are also giants whose “height” reaches one meter.
The smallest sea anemone discovered by scientists is considered to be the Gonactinia prolifera sea anemone; its height is only 2 millimeters.
These animals are widespread in all oceans and seas; the greatest species diversity is manifested in the tropical and subtropical zones. Sea anemones have acclimatized even in the icy waters of the Arctic Ocean.
According to their feeding method, sea anemones are predators. Some species swallow everything into themselves (both stones and paper), others, after accidentally swallowing an extra object, spit out the unnecessary.
The sea anemone received its second name - sea anemone - for its extraordinary beauty. This sea creature really does look like a beautiful flower. Unlike other coral polyps, the sea anemone has a soft body. According to the biological classification, sea anemones are a type of coelenterates, a class of coral polyps. They are closely related to jellyfish.
The sea anemone has a soft body compared to other corals.
Description of sea anemone
To determine whether an anemone is an animal or a plant, it is necessary to study the features of its structure. Sea anemone belongs to the animal kingdom. Its body has a cylindrical shape. On top it is decorated with a corolla of tentacles.
External features
Sea anemones come in a variety of colors. In nature there are varieties of all colors and shades. Many varieties have contrasting tentacle colors, which makes these animals even more attractive.
The sizes of these coelenterates are also strikingly diverse:
- the height of the gonactinium does not exceed 3 mm;
- the diameter of the carpet anemone reaches 1.5 m;
- The height of the Metridium salami species can be up to 1 m.
Body structure
The main part of the body - the leg - consists of muscles that are located in a ring and longitudinally. Thanks to the contractions of these muscles, the polyp can bend and change its length. On the lower part of the leg there is a so-called sole. Its surface is structured differently in different species. Some “root” in loose soil with the help of their soles, while others secrete a special substance with which they attach to hard surfaces. In the genus Minyas, the sole is equipped with a pneumocystis - a special bladder that acts as a float and allows the sole to float upward.
The muscle fibers of the leg are surrounded by the intercellular substance mesoglea, which has a dense cartilaginous consistency and gives the body elasticity.
On the upper part of the body there is an oral disc, around which tentacles are located in several rows. In one row all the tentacles are the same, but in different rows they can differ significantly in appearance and structure. Each tentacle is equipped with stinging cells that release thin poisonous threads.
The oral disc leads into the pharynx, and from there a passage opens into the gastric cavity - a primitive resemblance to the stomach. The nervous system of the sea anemone is very simple, it is represented by clusters of sensory neurons around the oral disc and in the sole area:
- nerve cells around the sole react only to mechanical impact;
- accumulations around the mouth opening and tentacles distinguish the chemical composition of the substances.
Habitats
Sea anemone is a coelenterate organism distributed throughout the world. Most species can be found in tropical latitudes, but some species live even in the polar regions, where the ambient temperature is very low. The species Metridium, or sea pink, lives in the Arctic Ocean.
The depth of the animal’s habitat is also striking in its diversity. Sea anemone can live both in the surf zone, where it falls on land at low tide, and in the very depths of the seas and oceans. Some species have adapted to survive at depths of more than 1000 meters. In the waters of the Black Sea, 4 species of these polyps were found, and in the Sea of Azov - 1 species.
Shallow-water inhabitants often rely on photosynthesis as microscopic algae take up residence in their tentacles. These species are common in places with good lighting and are active during daylight hours.
Other varieties, on the contrary, do not like bright light and tend to go deeper.
Lifestyle and nutrition
Sea anemone feeds on organic food. These polyps can catch and perceive their prey in different ways:
- some species swallow everything, including small pebbles and debris;
- some sea anemones throw out all the inedible objects that they come across;
- the largest and most predatory ones catch and kill small fish that happen to be nearby;
- some polyps live in symbiosis with algae and feed on them.
A “hungry” sea anemone opens its tentacle-rays wide and catches everything that floats past it. After the sea anemone has had enough, it rolls its tentacles into a ball and hides them. The same reaction is observed when it dries out or when danger approaches.
All sea anemones are usually divided into three varieties:
- sessile;
- floating;
- burrowing.
Sessile species are so named rather arbitrarily because they are able to move slowly. Polyps begin to move when they have little food, too little or too much light. Movement can be carried out in several ways:
- “somersaults” - when the sea anemone sticks to the ground with its mouth and tears off the leg, moving it to another place;
- alternately tearing off one or the other part of the sole from the soil;
- crawling, contracting different muscles of the body.
Burrowing sea anemones sit most of the time, buried in the ground so that only the corolla remains outside. In order to make a hole for itself, the animal takes water into the gastric cavity and pumps it, thus going deeper into the soil.
Floating species float on the water and surrender to the force of the current. They can move their tentacles rhythmically or use pneumocystis.
Polyps begin to move when they have little food, too little or too much light. Reproduction methods
Reproduction of sea anemones occurs in different ways. In the asexual method, the body of the polyp is divided longitudinally to form two individuals. The exception is Gonactinia - the most primitive species, which is divided transversely. In the middle of the polyp's stalk, a second mouth opening is formed, then two separate individuals are formed.
Some organisms reproduce by budding from the lower part of the stalk to form several new individuals.
These coelenterates are mostly dioecious, although it may be impossible to distinguish males and females from each other based on external characteristics. Sexual reproduction occurs in the following way:
- In the thickness of the intercellular substance, germ cells are formed.
- Fertilization can occur in the gastric cavity or in water.
- As a result, planulae (larvae) are formed, which are freely carried over long distances by the current.
Sea anemones can reproduce both sexually and asexually. Interaction with other organisms
Although sea anemones are a type of solitary polyp, in some situations these organisms can aggregate and form giant colonies. Most sea anemones are indifferent to their own kind, although some species can be very aggressive and quarrelsome.
Sea anemones can coexist very closely with other species of marine animals and plants. A common example is the symbiosis with the clownfish. The sea anemone “eats up” the prey after the fish, and the fish, in turn, cleans the polyp of debris and food debris.
Often small shrimps act as symbionts: they hide from enemies among the tentacles of the sea anemone and at the same time cleanse them of organic residues and debris.
Adamsia sea anemones can only live in symbiosis with hermit crabs, which attach polyps to their shells. In this case, the sea anemone is positioned in such a way that its oral disc is directed forward and food particles fall into it. Cancer, in turn, receives reliable protection from predators. By changing the shell, the hermit will transfer the sea anemone to the new “home”. If cancer somehow loses “its” polyp, it can even take it away from a relative. This existence benefits both species.
- Phylum: Cnidaria (Coelenterata) Hatschek, 1888 = Coelenterates, cnidarians, cnidarians
- Subphylum: Anthozoa Ehrenberg, 1834 = Corals, coral polyps
- Class: Hexacorallia = Six-rayed corals
- Order: Actiniaria = Sea anemones, sea flowers, sea anemones
Anemones, sea anemones - order Actiniaria
Sea anemones or sea anemones (Actiniaria) are an order of the class of six-rayed corals, subphylum Corals or coral polyps (Anthozoa). About 1,500 species of sea anemones are known. Sea anemones are quite large, fleshy animals, reaching a height of one meter. They have soft tubular bodies that are completely devoid of a calcareous skeleton.
The body of sea anemones is cylindrical in shape, truncated at the top. It has a slit-like mouth surrounded by rows of tentacles.
The body of sea anemones ends at the bottom with a “sole”, with the help of which the animal sticks, thus attaching itself to underwater objects.
At first glance, the similarity of the tentacles of sea anemones with the petals of flowers is striking, and most of all they resemble the flowers of chrysanthemums, dahlias and asters.
At the ends of the tentacles of some species of sea anemones, trapping threads are formed due to the formation of a large number of stinging capsules here.
At the same time, the stinging capsules serve the sea anemone both for attack and protection from enemies. The poison of the stinging threads, having hit the victim, instantly paralyzes it as soon as the sea beauty touches them with its tentacles. Even a person who unintentionally touches an anemone develops a burn on the skin, and the hand swells for a long period. In addition, there is a general intoxication of the body, which is accompanied by headache and chills. After some time, the affected skin dies at the site of the burns, and deep, poorly healing ulcers form.
At the same time, the poison of the stinging capsules of sea anemones is still not an absolutely reliable means of protection against enemies. Thus, some mollusks pursue sea anemones, since they are more or less insensitive or insensitive to their poison, and some types of fish easily swallow sea anemones without harming themselves. But many small fish are excellent food for predatory sea anemones.
The peaceful coexistence of this sea “flower” and some fish, which is often found in nature, is also well known. Clown fish live among the tentacles of sea anemones without the slightest harm to themselves.
Sea anemones feed mainly on various small invertebrates; sometimes their prey is fish, which they first kill or paralyze with the “batteries” of their stinging cells or cnidocytes, and only after that they pull them to their mouths with the help of tentacles. Large sea anemone species also feed on crabs and bivalves.
The edges of their mouth can swell, forming something like a lip, which also helps in capturing prey.
Sea anemones such as Metridium, Radianthus and Stichodactyla, which have numerous tentacles, feed mainly on food particles suspended in the water. But the anemone Stichodactyla helianthus is capable of catching sedentary sea urchins, enveloping them with its muscular oral disc. Those anemones that feed on particles suspended in water catch plankton inhabitants with the help of sticky mucus covering the surface of the body and tentacles. Cilia located on the surface of the body always direct prey towards the oral disc, and cilia on the tentacles move food particles to the tips of the tentacles, after which the tentacles bend and send food into the mouth.
Sexual reproduction is ensured by both dioecious and hermaphroditic sea anemones. The gonads are located on the septa, which look like longitudinal swollen cords lying between the mesenteric filament and the retractor muscle. Fertilization and development of eggs can occur both in the gastric cavity and in sea water during external fertilization. The planula larva, which can be planktotrophic or lecithotrophic, after a certain period of time (varies among different species), undergoes metamorphosis, turning into a new individual sea anemone.
About the animals included in the order Actiniaria. The name of the animals comes from the name of an earthly flower, anemone.
If you check the classification, sea anemones are included in the class Anthozoa, a phylum of cnidarians and a subclass of six-rayed corals. This animal is known to the world because of its symbiotic relationship with fish.
Sea anemones benefit from their association with fish - improved gas exchange and nutrition (the food that remains after the fish eat).
The same symbiosis has developed between sea anemones and crabs of the genus Lybia. Boxer crabs use the stinging polyps of sea anemones to protect themselves from predators. The crabs pick up sea anemones and hold them as a shield. Anemones, in turn, thanks to crabs gain mobility, because they cannot move independently.
Here are some interesting facts about sea anemone:
Sea anemones, like all other cnidarians, have mesoglea in their body - a jelly-like substance. Anemones have a close relationship with corals, hydra and jellyfish.
Sea anemones can decorate any aquarium. For commercial purposes, sea anemones are considered as aquarium collection. Thus, the sea anemone trade is increasing.
These sea creatures have an amazing range of color diversity. Their vitreous bodies are always bright and delicate.
Sea anemone size.
The diameter can reach 1.8 - 3 cm. The largest sea anemones have a span of 2 meters. The smallest ones barely reach 4 mm.
The sea anemone's mouth functions like an anus. Capture function and prey catching. The location of the mouth is the center of the disc cavity. And several tentacles located around the mouth.
Sea anemones are harmless and harmless animals. The sea anemone is not dangerous to humans. However, some sea anemone species have a toxin that can cause burns to humans.
Sea anemones feed on fish, shellfish and small sea animals. Peaceful sea anemones are calm individuals: they eat everything that floats in the water. However, they distinguish between edible food and inedible food.
- Next to sea anemones live those fish and shellfish that are insensitive to their poison.
- For large and predatory fish, sea anemones serve as a place of camouflage and shelter.
This animal, the sea anemone, has a completely different way of life from other cnidarians. They have the disadvantage of free swimming, as for example jellyfish do. They differ from corals in that they do not live in colonies or groups, but individually - they prefer to live alone.
Life cycle of sea anemone. The polyp arises from Planula after the egg, fertilized by sperm, begins its division.
Asexual reproduction is also characteristic of sea anemones. In some species of sea anemones, division is the result
asexual reproduction.
Most sea anemones live in one place permanently. However, they may move to another place if it is not suitable for them to live in. They move if predators harass them or the location encounters prolonged dryness. To get to a new place they use crawling-like movements.
Sea anemone can be eaten. It is used as a delicacy in southwestern Spain and southern Italy.
Sea anemones are often served battered or marinated in vinegar.
The animal sea anemone really looks like a flower. They were called anemones, but to some it resembles an aster. Explorers of the deep sea have counted one and a half thousand different species of anemones.
When cut into pieces, sea anemones demonstrate their remarkable ability to reproduce and regenerate.
In one row, all tentacles of an anemone are identical in color, structure and length. however, they may differ from row to row.
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