Toothless common, or river, often found at the bottom of reservoirs and lakes, where there is running and clean water. Usually snails are located at shallow depths. In sandy ponds, mother-of-pearl shells can often be seen. Individuals are very easy to find in nearby bodies of water, rivers or lakes. As a rule, they like to be located near coastline, plunging into the fine sand with the blunt end of the body. Usually only the rear pointed part is visible from the ground.
Toothless is found in bodies of water with running water
The structure and lifestyle of toothless
By appearance they resemble pearls. But toothless is larger, the shell structure is thinner. The difference from barley is that the first one has teeth on the back side that form a lock. Toothless has no pointed parts on the shell. Hence its name was formed - toothless. Barley can be found teeth if you open the shell .
The structure of the animal:
- The body of mollusks is covered with a shell, which protects the body of the host from predators.
- It consists of two doors, or halves, which fit snugly together.
- The shell has a slight expansion towards the frontal edge, and its posterior part is narrow.
- If the mollusk has just been caught, then its doors are tightly interconnected. Thus, the animal is protected.
- To open the shell, a knife is inserted between the valves, and two muscles are cut that are attached to the shell at the rear and front ends.
- When the muscle contracts, the valves close.
The opening of the mollusk occurs with the help of a tight ligament that runs along the upper side of the shell. While the mollusk is alive, its valves are covered. But as soon as the animal dies, its muscles come to a relaxed state, and the shell opens.
Move and sink
The leaf has a three-layer structure: mother-of-pearl, porcelain and horn. Externally, the carapace is covered with a white lime layer, then comes porcelain, which has a coating of dark coffee or green color, and then follows the stratum corneum. The mother-of-pearl part is inside, it consists of small plates that are located one above the other. The layer shines beautifully, shimmers with multi-color shades. Shell growth occurs faster in summer than in winter.
On the plane of the stratum corneum, wide summer and narrow winter stripes of growth are found. It is in these areas that the age of the mollusk is determined.
The inside of the shell shell - mother-of-pearl layers To notice how the animal moves, it descends into the terrarium, where there is sand at the bottom. After some time, you can notice that the walls gradually open, and a thick muscular outgrowth is exposed through the gap. It's called the clam leg. Usually a large outgrowth. When the leg protrudes from the shell, the toothless digs the soil under itself, plunges into the dug hole with the help of the front end.
With the help of the leg, the mollusk moves along the bottom of the reservoir. If the river is shallow, then traces of mollusks are visible on the sandy bottom. They are arranged in the form of small strips, as if someone ran their fingers over the sand. Toothless are a sedentary animal species. Usually they have sedentary image life. In an hour, the mollusk crawls no more than 35 cm.
Nutrition and the mantle cavity
Toothless common feeds on small parts of the remains of animals and plants that are in the reservoir. Together with the liquid, the smallest particles end up in the mantle cavity. At the front end of the valves of the animal there is a mouth, which is surrounded by two rows of soft leathery folds - these are horny lobes. By moving the blades and the cilia covering them, the food is in the mantle plane of the core, and from there it enters the digestive organs. Toothless is not a predator.
If you open both flaps of the toothless, then you can find two displaced folds of the skin on the sides. They cover the body from the sides, while resembling a mantle.
The gap between the body of the river mollusk and the mantle is called the "mantle cavity". It contains the organs of the shell. They can be clearly seen if the mantle cavity is moved aside. Bivalves have a soft body, so they are called "mollusks" or "soft-bodied".
Toothless is not a predator
In the back of the sash, the toothless do not fit closely to each other. They do not close in the place where the parts of the mantle are located. There are two holes between them. Pure water enters the body of the animal through the lower cavity. It pours out through the top hole. The animal lives in a place where there is water circulation, so the mollusk is in constant fluctuation of multiple cilia, which are located on the internal organs of the animal.
Breathing and nervous system
Many animal lovers are interested in the question of what the toothless breathes. On the sides of the body, behind the leg, in the mantle cavity are its paired respiratory organs, which are called gills. They are brown in color. The water that ends up in the mantle cavity brings oxygen, which is dissolved in water. At the same time from the gills to aquatic environment habitation, carbon dioxide is released, which accumulates in the primary body of the mollusk.
Description nervous system toothless is very simple. It consists of 3 pairs of nerve nodes, which are interconnected by nerve endings. The animal senses irritation. If you touch an open sink, it will immediately close.
If the mollusk is kept at home, then it is very sensitive to the water in the aquarium. If the toothless is in a terrarium, then chemistry cannot be added to the water, otherwise the animal will immediately die from this. And also the mollusk likes to have a large amount of dissolved oxygen in the water. Algae must necessarily grow in the terrarium, and you also need to put a special device in the water that will create forced aeration.
The body of the mollusk contains a lot of iodine, zinc and other necessary elements for the full development of fish. Usually, before serving the fish, the mollusk is crushed. If you get a toothless as a pet, then with proper care she can live more than 2 years.
When moving in an artificial reservoir, the mollusk plows the sand, plants can be damaged if they have a weak root system. The way out of the situation is to plant algae in special pots. Optimum temperature water for a clam is 20 or 25 degrees Celsius. Before placing a mollusk in an artificial reservoir, he needs to be quarantined, acclimatize to an unknown environment. It does not matter where the animal was purchased: in a pet store, grown in an aquarium or caught in a natural reservoir.
You need to quarantine for 12 hours, after which aquarium water is added in small quantities to a separate container. The adaptation period is 8 days. At this time, the water should be well aerated. If the toothless is located in an artificial reservoir, then its condition must be constantly monitored. A dead snail can be recognized by its wide open shells. It is not recommended to place river mollusks in an artificial reservoir, because it will be difficult for them to have an adaptation period. In addition, river mollusks in captivity will not live long.
Reproduction and compatibility
Animal excrement contains phosphorus and nitrogen - this causes the active growth of aquatic plants. Therefore, experts do not recommend keeping a lot of toothless in one aquarium. Animals do not tolerate planaria worms. They can be introduced into the aquarium through contaminated soil, live food or plants. Planarians eat toothless larvae, and can also get stuck in the gills of adults, thereby causing suffocation in the latter. Toothless are dioecious, but in appearance, boys cannot be distinguished from girls.
Characteristics and description of species
Now experts have more than 50 species of mollusks. Among them is an ordinary toothless or swan, duck, narrow. Characteristics of other species:
- An ordinary toothless grows no more than 20 cm in length, has thin walls.
- The duck mollusk reaches a length of no more than 15 cm.
- Narrow toothless refers to more rare species, differs from the rest in flat shells.
In the reservoirs of Russia, in addition to the common toothless, other species of individuals can be found. Common pond snail, common amber, common shutter.
Prudovik belongs to the class of gastropods
Detailed description types:
- The common pond snail is a representative of the species of mollusks, which is classified as a class of gastropods. characteristic feature the pond snail is its method of locomotion in the water. He has a special organ called "leg". During movement, the leg is aimed upwards, while protruding slightly above the surface of the reservoir. To prevent the individual from drowning during movement, the middle of the leg bends down, forming the shape of a boat. And at the same time, the shell is directed downward. Such an original movement is not fully understood by scientists. The size of the pond snail reaches 5 or 8 cm. The color of the shell has a changing color from dark brown to yellow, and its structure is thin and transparent. Prudoviks are classified as mollusks, they eat both animal and plant foods. But mostly used as food aquatic plants, leaves and algae.
- Amber ordinary belongs to the pulmonary subclass of molluscs, belongs to the family of ambers. Adult individuals reach a length of up to 22 mm.
- The common shutter is very small, its dimensions do not exceed 1 cm. The difference between the shutters is that their breathing occurs with the help of porous gills. Therefore, animals are classified as pulmonary species.
Toothless is an interesting animal species that is often found at the bottom of Russian water bodies. Their mother-of-pearl shells are hard to miss. They live well not only in wild waters, but also in home aquariums.
Presented in domestic reservoirs. This species lives mainly on sandy and muddy bottoms. Let's take a closer look at the structure of the toothless shell, find out what lifestyle this mollusk leads.
Structure
Considering the structure of the toothless shell, the outer and inner layers, it is worth noting that such a mollusk is extremely similar to another common mollusk in our reservoirs - barley. The shape of the shells of these species is almost identical. However, toothless are more massive, and also have a fine structure of the outer shell. In addition, these creatures do not contain teeth on the inside of the shell, forming a kind of lock, like a barley. Hence the name - toothless.
Looking at what a toothless shell looks like, external structure shell, it should be noted that the latter is formed from two keratinized halves tightly adjacent to each other. In front of the sink has an extension. It narrows in the back. In a live, freshly caught mollusk, the valves are always securely closed, which is a protective reflex against predators.
To consider internal structure Toothless shells, you will have to cut the internal muscles that hold the shell closed. In the natural environment, the shell opens by contraction of a strong horn-shaped ligament that runs along the entire dorsal part of the body of the mollusk. While the toothless is alive, its protective shell remains closed most of the time. When the animal dies, the muscles relax and the valves open voluntarily.
What is a toothless shell?
It should be noted that the structure of the shell of toothless and pond snails, as well as the same pearl barley, is almost identical. The outer shell of the mollusk is, in fact, a keratinized calcareous layer, covered with a brownish, petrified silty coating. If a piece of shell is placed in a solution of hydrochloric acid, gas bubbles will begin to actively stand out from the material. This indicates the organic structure of the outer shell of the mollusk.
Studying the toothless structure, you can see that inside the shell there is a mother-of-pearl layer, which looks like thin plates overlapping each other. The shell surfaces here have an attractive iridescent sheen.
In general, the keratinized part of the body of the mollusk consists of three layers. The outer part of the shell is formed by a keratinized calcareous layer. From the inside, the toothless carapace is lined with a porcelain and mother-of-pearl layer.
soft tissues
Exploring what the toothless are, the structure of the mollusk, one should talk about the internal, mantle cavity of such an animal. Opening the shell flaps, one can see folded skin structures that are located on both sides of the body. The edges of such soft tissues smoothly pass into the shell and are connected to the keratinized structures with strong ligaments.
The structure of the toothless external is represented by structures that are sufficiently resistant to mechanical stress. In turn, the inside of the mollusk is extremely soft. For this reason, such animals are also called soft-bodied. In the mantle, folded cavity are internal organs. To see them, it is enough to unscrew the soft tissues.
The shell valves in the posterior part of the body of the mollusk do not fit together tightly. There is a small gap through which fresh water enters the sink. The liquid is filtered out by the digestive organs of the toothless and brought out through a special upper opening on the body. The movement of water in the mantle cavity is supported by the rhythmic vibrations of the so-called ciliated cilia that cover the internal organs of the mollusk.
Breathing and nervous system
In the mantle cavity of the mollusk there are gills. They can be distinguished from other soft tissues by their characteristic brown hue. Each inner side of the shell contains a pair of gills. The water that enters the sink brings toothless not only nutrients, but also oxygen.
As for the nervous system, in toothless it is primitive and consists of several pairs of nerve nodes. With the help of nerve fibers located in soft tissues, the mollusk perceives stimuli and responds to them. So, when touching an open shell, its valves will instinctively close.
Reproduction features
Toothless are heterogeneous creatures. Outwardly, females are no different from males. During the mating season, molluscs concentrate in a certain area of the reservoir. The males release the seed into the water. Spermatozoa enter the body of females through a special siphon, after which the fertilization of eggs begins. The latter develop into larvae. Through the same siphon, not yet fully formed individuals are thrown out.
Lifestyle
Toothless, the structure of which was described above, lead. Such mollusks feed passively. Toothless filter out primitive organisms and plant particles from the water. The latter enter the mantle cavity through the oral lobes - small leathery folds located in the front of the body. The movement of shimmering eyelashes useful material are driven into the digestive organs.
To follow the toothless and behavior in the natural environment, it is enough to place the mollusk in an aquarium that has a sandy bottom. After some time has passed, you can notice the separation of the shell valves. A leathery fold will look out through the gap formed, thanks to which the animal moves along the bottom. By itself, toothless leaves shallow grooves on the surface of the sand. Within an hour, the mollusk is able to cover a distance of no more than 30-40 centimeters.
Finally
As you can see, toothless are typical representatives of primitive bivalves. Such animals massively settle in ponds and rivers, since they do not have natural enemies. Unlike the same oysters and mussels, toothless are not eaten by humans.
Toothless common(river toothless) - lat. Anodonta cygnea. Toothless can often be found at the bottom of lakes and rivers with clear running water at shallow depths. On the banks of sandy reservoirs, it is easy to notice the mother-of-pearl shells of these invertebrates. Live shellfish are easy to find nearby. Usually they sit in the water near the shore, buried in the sand with the blunt front end of the body, and only the rear pointed part protrudes from the sand.
Structure
In appearance, toothless are very similar to barley. Toothless appear slightly larger in size with a thinner shell structure. Their main difference lies in the fact that in the river barley, the shell valves have teeth on the dorsal side from the inside, forming a lock, which the toothless does not have. This is where the name "toothless" comes from. The teeth of the barley can be seen only by opening the shell.
The body of a toothless, like a grape snail, is covered with a strong shell, which protects the animal from predators. The shell of a toothless tooth consists of two halves, or flaps, tightly adjacent to each other. Towards the anterior end, the shell expands, and somewhat narrows towards the posterior end. In a freshly caught live mollusk, the valves are tightly closed. So he is protected. To open the shell, it is necessary to insert a thin blade between the valves and cut two strong muscles attached to the shell valves at its front and rear ends. By contracting, these muscles close the valves. The shell opens due to a strong, horn-shaped, elastic ligament passing along the dorsal side of the body from the inner surface of one valve to another. While the toothless is alive, the valves are mostly closed. But when the animal dies, the muscles relax and the shell opens.
Sink
If a piece of toothless shell is lowered into hydrochloric acid, it will hiss, gas bubbles will begin to stand out from it. Outside, this white calcareous, porcelain layer is covered with a dark, brownish-greenish stratum corneum. The mother-of-pearl layer lining the inside of the toothless shell consists of the thinnest plates overlapping one another. They have a beautiful reflection, shimmering with all the colors of the rainbow. Thus, each leaf consists of three layers: horn, porcelain and mother-of-pearl.
In summer, the toothless shell grows faster than in winter. Therefore, wide summer and narrow winter bands of annual growth can be seen on its surface. From these bands, you can approximately determine the age of the animal.
mantle cavity
Having opened both valves of the shell, one can see that two folds of skin hang down on the sides of the body of the mollusk. They cover the entire body from the sides, reminiscent of ancient clothes - a mantle. Therefore, the mentioned folds were called the mantle. The edges of the mantle pass into the shell.
The space between the body of the mollusk and the mantle is called the mantle cavity. Toothless have a soft body. Therefore, such animals are called soft-bodied, or mollusks. In the mantle cavity are the internal organs of the mollusk. They can be seen only by rejecting the mantle.
From the back of the mollusk, the shell valves do not fit tightly to each other. The halves of the mantle do not stick around tightly in this place either. There are two holes between them. Through the lower inlet, fresh water enters the mantle cavity. Through the upper outlet, it enters the outside. The constant movement of water is supported by continuous fluctuations of numerous shimmering cilia covering the internal organs of the animal.
Breathing and nervous system
On the sides of the body of the toothless, behind the leg, in the mantle cavity are placed the respiratory organs - gills. They are brown. There are a couple of them on each side. Water entering the mantle cavity all the time brings oxygen dissolved in water to the gills. Carbon dioxide is released into the water from the gills, which is formed in the body of the mollusk.
The nervous system of the toothless consists of three pairs of nerve nodes interconnected by nerve fibers. With the help of the nervous system, toothless, like other animals, perceive irritations and respond to them. If you touch an open clam shell, it immediately closes.
Food and movement
Toothless feed on microscopic animals and plants, as well as the smallest remains of animals and plants in the water. Together with water, these nutrient particles enter the mantle cavity.
At the front end of the toothless body is a mouth surrounded by two pairs of small soft leathery folds - oral lobes. With the movement of the blades and the cilia covering them, food is driven from the mantle cavity into the mouth, and from there into the digestive organs.
To see how the toothless moves, you need to lower it into an aquarium with a sandy bottom. After a few minutes, you can notice that the shell valves are gradually moving apart. A thick muscular outgrowth protrudes through the gap. This is the animal's leg. It can greatly increase in volume. Having stuck out its leg, the toothless begins to slowly dig sand under itself and gradually deepens into the dug hole with its front end. With the help of the foot, this animal moves along the bottom. In a shallow pond on a sandy bottom, you can often see traces of toothless. They have the appearance of shallow grooves, as if they were being run through the sand with a finger. Toothless are sedentary animals, leading a predominantly sedentary lifestyle. In an hour they crawl no more than 25 - 30 centimeters.
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 Photo 1. Common European toothless - Anodonta cygnea |
 Photo 2. Common European toothless - Anodonta cygnea |
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Toothless ordinary belongs to the subfamily Bezubok (Anodontinae) of the family Unionidae (Unionidae) of the class Bivalvia mollusks (Bivalvia). The subfamily toothless is characterized relatively thin shells, devoid of locking teeth.
Synonyms. Toothless common, or European, or swans - Anodonta cygnea (Linnaeus, 1758), = Anodonta mutabilis, = Mytilus cygneus Linnaeus, 1758, = Anodonta cellensis Schroter, 1779, = Mytilus zellensis Gmelin, 1791, = Anodonta ventricosa C. P25 , = Anodonta elongata nob. Potiez & Michaud, 1844.
Origin of name. The name of these mollusks, both Russian and Latin, is associated with the absence of locking teeth on the shell.
Appearance. Sink common toothless large, elongated-oval (its height is 0.5 length), slightly angular, relatively thin-walled, brittle. Growth lines clearly expressed, rough along their entire length, the epidermis between them is smooth, shiny, finely concentrically striated. Shells grey, olive brown or almost black colors. With a light coloration of the shell, radial rays are noticeable, which diverge from the top to the edges of the valves. Thickness shell valves is the same in the direction from the umbo to the ventral margin.
Dorsal and abdominal the edges the shells are straightened and parallel to each other (the shell diagram with the designation of sides and edges is shown in the description of the Bivalve class). The back edge creates a wide, blunt beak that connects to the top edge with a straight or concave line. crowns(apices) narrow, not protruding, lying from the anterior end of the shell for 0.25-0.3 of its length. Their sculpture is composed of 5-6 rows of weakly sinuous concentric folds, more or less straightened in the middle.
Ligament(ligament connecting the valves) long, wide, massive. Shield laterally constrained, protruding, pronounced, although the radial angles that separate it from the rest of the valves are indistinct. Shield inconspicuous.
Inner surface the sash is smooth, nacre thin, brittle, blue, irradiating. mantle line deep enough.
Toothless is a very variable species, forming in almost every large body of water, area, etc. various morphs, ecological races, varieties (see below - Features of taxonomy and other species).
Dimensions. The common toothless is the largest of our toothless, the length of the shell of an adult mollusk lies within 8-12 cm (the maximum mention is up to 20 cm), the height is 42-63 mm, the convexity is 26-46 mm.
Traffic. Toothless movements are rather monotonous - they can dig into the sand with the help of rhythmic contractions of their legs, and also crawl along the bottom soil. Movement is carried out with slightly open sides, ventral side down, umbo up (the shell diagram with the designation of sides and edges is shown in the description of the class of Bivalves), into the gap between which the mollusk sticks out its leg, with the help of which it slowly crawls along the bottom. At the same time, characteristic deep furrows remain on sandy or silty soil, which are clearly visible in shallow water. The speed of movement is low - 20-30 cm per hour.
Breath. Like all bivalves, toothless mollusks breathe with gills, which are paired lobes on either side of the leg. In a calm state, when toothless is at the bottom, with the ventral side (half-open valves) down, water is sucked into the mantle cavity through the inlet (lower) siphon, washes the gills and is thrown out with force through the outlet (upper) siphon (a detailed description of the breathing process with illustrations and the scheme of water flows is given in the description of the Unionid family - Unionidae).
Food. Toothless are filter feeders, their food is carried out simultaneously and in parallel with respiration - the water current drawn into the gill cavity carries with it small nutrient particles suspended in water - zoo- and phytoplankton, as well as detritus. The mollusk swallows them, driving them into its mouth opening with the help of soft outgrowths, which are called oral lobes and sit in the amount of two pairs at the front end.
Habitat. The common toothless is found in a variety of water bodies, large and small, stagnant and flowing. Prefers lakes, reservoirs, ponds, oxbow lakes, canals and slowly flowing rivers. Keeps on organic-rich silty and sandy-silty soils. Normal feeding depth - 0.5-2 m
Spreading. The common toothless is one of the most widely distributed types of toothless. It is common in Central and Northern Europe, in the European part of Russia and countries former USSR, as well as in Western Siberia, Western and Central Asia.
Features of taxonomy and other types. The common toothless is a rather variable species, forming various morphs, ecological races, and varieties in almost every large body of water, geographical region. According to various classifications, they are considered either subspecies of the common toothless, or certain types. It:
- elongated or elongated toothless (Anodonta cygnea cellensis, = Anodonta cellensis Gm., = Anodonta zellensis) - the shell is long, its rear end forms a narrow beak 12-16 cm long, lives in lakes and river oxbows,
- toothless fish (Anodonta cygnea piscinalis, = Anodonta piscinalis Nils.) - wide, angular, with a sharp posterior edge and almost straight dorsal, up to 110 cm long,
- toothless duck (Anodonta cygnea anatina, \u003d Anodonta anatina L.) - smaller, up to 8 cm long, resembling an ordinary and fish in shape.
Other descriptions. Catching a toothless fish is not a big deal, especially if the water is clear enough and the shells can be seen from the shore. For fishing, you need a net with a sufficiently strong rim, which can act like a rake, raking the ground and picking up mollusks released from sand and silt into the net.
The toothless shell consists of two convex valves, which, like strong shields, cover the delicate soft body of the mollusk, protecting it from adversity and danger. The valves are connected to each other by a hinge ligament-ligament (on the dorsal margin of the shell). The opposite edge is called the ventral. The blunt rounded edge of the shell is its anterior end; the rear end is sharper, elongated. From above, the shell is brown-green or brown-yellow; the color depends on the horny substance covering it from the outside. If you scrape the shell with a knife, it is easy to see that the dark stratum corneum comes off, and under it you can see a white substance - a porcelain layer. From the inside, the shell is lined with a brilliant layer of mother-of-pearl, which is easy to see when you find an empty shell of a dead shell.
Let's try to open tightly closed doors. This is not without difficulty, and the resulting gap immediately closes again. The valves are held by the work of strong closing muscles at the anterior and posterior ends of the shell. When opening the shell, the mantle of the animal is striking - a yellow mucous lining that covers the inside of the shell valves.
It is not difficult to observe the movements of the toothless by putting it in a vessel with water and leaving it alone for a while. After some time, the shell flaps will slowly open, forming a gap through which a soft, yellowish, blunt process will stick out - the leg of the mollusk. With the help of this process, the mollusk can dig into the sand with its front end or slowly crawl along the bottom, leaving behind characteristic furrows in the sand. The speed of this movement, however, is very insignificant: hardly more than 20-30 cm per hour.
Toothless breathing can be observed on an excursion only if you manage to notice a mollusk half-burrowed in the sand in the shallow water, which remained undisturbed. Having put its rear end out of the ground, a calmly sitting animal opens two short tubes on it, formed by the edge of the mantle: an inlet siphon, with black fringed edges, through which water enters the gill cavity of the mollusk, washing the gills, and an excretory siphon, through which the waste water is displaced .
The flow of water is created by the beating of cilia covering the inner sides of the mantle and gills. Driven by cilia, water enters the mantle cavity to the mouth opening, is driven into it, enters the digestive system. Respiratory processes are carried out simultaneously with nutrition. If you open the valves of the caught toothless and insert wedges (from a stick or cork) between the valves, then in the open gap you can see delicate transversely striated brown-yellow gill plates, in pairs on each side of the body. The water entering through the siphon washes the gills, which absorb the oxygen dissolved in it and release carbon dioxide, which is removed with the flow of water through the excretory siphon.
On the tour, you can also observe some of the reproduction of toothless. Quite often there are mature females in which the gill plates are significantly swollen. These are females carrying embryos that develop in the cavity of the external gill. It is worth breaking through or cutting through such a gill, as a thick brown mass will come out of the hole, which seems fine-grained to the naked eye. It consists entirely of living toothless larvae, the so-called glochidia, which can only be seen through a microscope.
Species descriptions and illustrations are taken from computer identification of freshwater invertebrates in Russia(Bogolyubov A.S., Kravchenko M.V., Moscow, "Ecosystem", 2018) .
Species descriptions and illustrations are taken from computer identification of freshwater invertebrates in Russia(Bogolyubov A.S., Kravchenko M.V., Moscow, "Ecosystem", 2018) .
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