Gastropods are the most numerous and diverse group of mollusks. It has about 90,000 species living in the seas, fresh water oh, on dry land. Most of them have a one-piece shell.
One of the representatives of this class lives in lakes, ponds and river backwaters - big pond snail about 5 cm in size.
External structure
In the pond snail, all three parts of the body are clearly distinguishable: head, leg and bag-shaped body. The top of the body is covered with a mantle. The pond snail has a spiral, twisted in 4-5 turns shell that protects the body of the animal. The shell is made of lime and topped with horn-like organic matter. In connection with the spiral shape of the shell, the body of the pond snail is asymmetric, since in the shell it is also curled into a spiral. The shell is connected to the body by a powerful muscle, the contraction of which draws the animal into the shell.
The leg of the pond snail is well developed, muscular, has a wide sole. The animal moves slowly sliding over plants or soil due to wave-like contraction of the leg muscles. The abundant mucus secreted by the skin glands of the foot facilitates smooth gliding.
Internal structure
Digestive system
In the mouth, on a special mobile outgrowth resembling a tongue, there is a grater with horny teeth. With their help, the pond snail scrapes off the soft parts of plants and microscopic algae deposits on underwater objects. There are salivary glands in the pharynx, the secret of which is processed food.
From the pharynx, food enters the stomach through the esophagus. The ducts of the liver flow into it. The stomach passes into the intestine, which makes several loops and ends with an anus at the front end of the body above the head.
Respiratory system
The body of the animal is covered with a mantle on the outside and closely adheres to the inner surface of the shell. Part of the mantle forms a kind of lung, numerous blood vessels develop in its walls, and gas exchange occurs here. The pond snail breathes atmospheric oxygen, so it often rises to the surface of the water and opens a round breathing hole on the right at the base of the shell. Next to the lung is the heart.
Circulatory system
The circulatory system is open, the blood is colorless. The heart consists of two sections - the atrium and ventricle, and blood vessels. Blood flows not only through the vessels, but also in the cavities between the organs. A large vessel, the aorta, departs from the heart. It branches into arteries. Then the blood enters the small cavities among connective tissue. There, the blood gives off oxygen, is saturated with carbon dioxide, enters the veins and goes through them to the lung.
Here the veins branch into numerous small vessels - capillaries. The blood is enriched with oxygen and gets rid of carbon dioxide. Blood rich in oxygen is called arterial, and poor in oxygen and saturated with carbon dioxide is called venous. Then the blood is collected in the veins and enters the heart. It contracts 20-40 times per minute.
excretory system
Due to the asymmetry of the body, the pond snail retains only the left kidney.
At one end, it communicates through a wide ciliated funnel with the pericardial sac, where waste products accumulate, and at the other, it opens into the mantle cavity on the side of the anus.
Nervous system
The nervous system of molluscs is scattered-nodal type. It consists of five pairs of nerve nodes (ganglia), interconnected by nerve bridges, and numerous nerves.
In connection with the twisting of the body, the nerve bridges between some nodes form a cross.
sense organs
On the head of a pond snail, there are organs of touch - tentacles, there are also tactile cells in the skin. The pond snail has one pair of tentacles. There are eyes - they are at the base of the tentacles. There are also organs of balance.
Reproduction. Development
Fertilization in the pond snail is internal. This animal is a hermaphrodite. The single gonad produces both sperm and eggs. They reproduce by eggs that are laid on aquatic plants or other objects. Fertilized eggs are covered with a common mucous membrane, securely attached to the substrate. Each animal lays about twenty clutches during the year.
After twenty days, tiny animals appear from the eggs. They grow rapidly, eating plant foods.
The pond snail becomes sexually mature at the end of the first year of its life. It is also interesting that when the reservoir (in which pond snails are found) dries up, not all mollusks die. Some secrete a dense film that closes the opening of the shell. In this state, the pond snail can live without water for about two weeks.
Well, we got to the most ambiguous aquarium snail, namely the pond snail. I know that 99% of aquarists not only dislike them, but hate them with fierce hatred for their voracity and fertility. However, it is still worth talking about the pond snail (more precisely, pond snails).
A bit of biology
Pond snails are a family of snails from the Pulmonata order, which, according to different classifications, includes from one (Lymnaea) to two (Aenigmomphiscola and Omphiscola) or several genera (Galba, Lymnaea, Myxas, Radix, Stagnicola), which differ mainly in the structure of the reproductive system. In appearance (by shells), representatives of these genera differ little from each other. In our review, we provide descriptions of the seven most common types of pond snails in central Russia. To avoid confusion, we indicate their species names according to the traditional classification, according to which all pond snails belong to the same genus Lymnaea. However, in the description of individual species, information is provided on modern views on their taxonomy, along with their new names.
All pond snails have a well-developed shell spirally twisted to the right (see how to determine the twist) by 2-7 turns (see photos and drawings). At different types In pond snails, it is of different sizes and shapes - from almost spherical to highly conical, with a more or less high curl, with a very extended last whorl. Most are light horn, horn, brownish horn, brownish brown, or black brown. Most often, it is thin-walled, slightly transparent and more matte, tower-shaped or ear-shaped; the mantle almost does not emerge from the mouth.
The body of pond snails is right-handed, thick, their head is wide, transversely cut; respiratory and genital opening on the right side. The visceral sac is in the form of a conical spiral. The tentacles are flat, triangular in shape, short and wide. The leg is rather long and massive. Its sole is elongated-oval. There is a short siphon formed by the outer edge of the mantle.
The pharynx of the pond snail is a muscular sac that passes into the esophagus, then into the goiter and stomach; the latter consists of a bilobed muscular section and an elongated pyloric section; a muscular stomach is characterized by a rough structure and contributes to the crushing of captured food; in the pyloric stomach and in the intestine leaving it, food is digested; the anus opens at the mouth of the shell.
When observing a pond snail in an aquarium, one can see how it sticks out the front part of the body from the shell and slowly slides along the glass walls. In this protruding part of the body, one can distinguish the head, clearly separated from the rest of the body by the neck interception, and the leg, a large muscular organ of movement of the pond snail, occupying the entire abdominal part of its body. On the head are triangular movable tentacles, at the base of which eyes sit; on the ventral side of the head in its front part, a mouth gap is placed. The movements of pond snails are of three types - sliding along surfaces with the help of a foot, ascent and immersion due to the pulmonary cavity, and sliding from below along the surface film of water.
The movement of the pond snail along underwater surfaces can be well traced when it crawls along the glass wall of the aquarium. It is caused by muscular contractions, undulating and evenly running along the sole; these movements have a fine adaptability, which allows the mollusk to move along thin twigs and leaves of aquatic plants.
Ascent to the surface and immersion to the bottom is carried out due to the filling and emptying of the lung cavity. With the expansion of the cavity, the cochlea floats to the surface without any push along a vertical line. For an emergency dive (for example, in case of danger), the pond snail pushes out the air in the lung cavity and falls sharply to the bottom. So, for example, if you prick the tender body of a mollusk floating on the surface, then the leg will immediately be drawn into the shell, and air bubbles will escape through the respiratory hole - the pond snail will throw out all its air ballast. After that, the mollusk will drop sharply to the bottom and will no longer be able to rise to the surface otherwise than by crawling along underwater surfaces, due to the loss of its air float.
The third way of movement is sliding along the lower surface of the water. When ascending, the pond snail touches the surface tension film with the sole of the foot, then abundantly secretes mucus, straightens the leg, slightly arching the sole inward in the form of a boat and, contracting the muscles of the sole, slides over the surface tension film covered with a thin layer of mucus.
Like other lung snails, pond snails lack primary gills and breathe atmospheric air with the help of a lung, a specialized section of the mantle cavity, which is adjacent to a dense network of blood vessels. In order to renew the air in the lung cavity, they periodically rise to the surface of the water. Having risen to the surface, the pond snail opens its respiratory opening, which is located on the side of the body, near the edge of the shell, and air is drawn into the vast lung cavity. At this time, you can hear a characteristic squelching sound - the "voice of a mollusk" - this is the opening of the respiratory hole leading to the mantle cavity. In a calm state, the respiratory opening is closed by the muscular edge of the mantle.
The frequency of lifting for breathing depends on the temperature of the water. In well-heated water at a temperature of 18°-20°, pond snails rise to the surface 7-9 times per hour. As the water temperature drops, they begin to rise to the surface less and less often and in autumn, long before the water body freezes at a temperature of 6 ° -8 ° C, due to a general drop in activity, they cease to rise to the surface at all. While photosynthesis of aquatic plants continues, pond snails consume oxygen bubbles on plants for respiration, and then stop filling the mantle cavity with air. At the same time, it either subsides or fills with water - a paradoxical, rare fact in nature, when the same organ alternately functions either as gills or as a lung.
In addition to breathing air or water, flowing in the cavity of the lung, the pond snail also lives due to skin breathing, which is carried out by the entire surface of the body washed by water; wherein great importance have cilia of the skin of the pond snail, the continuous movement of which contributes to the change of water washing the surface of the body of the mollusk.
Prudoviks are omnivores, but in nature they prefer plant foods. Slowly crawling, they scrape off algae raids from various objects submerged in water, for example, from the surface of the stems and leaves of higher aquatic plants. If algae become scarce, they also consume living plants - leaves and stems of aquatic plants, choosing the most tender of them, as well as plant detritus.
To scrape food, pond snails use a toothed grater - a horny plate that fits in the pharynx on a tongue-like elevation. The plate of the grater from the surface is seated with rows of cloves. The nature of the grater is easy to observe in the aquarium, when the pond snail crawls over the glass and from time to time sticks the grater out of its mouth and runs it over the surface of the glass to scrape off the layer of green algae that has developed on it. Pond snails sometimes use animal food - they devour the corpses of tadpoles, newts, fish and mollusks, scraping them from the surface, small invertebrate animals.
Lifestyle. At the height of summer, pond snails stay near the surface of the reservoir, and sometimes even on the very surface of the water. To catch them, there is not even a need to use a net, they can easily be removed from underwater objects by hand.
When water bodies inhabited by pond snails, such as small lakes, ditches and puddles, dry out, not all mollusks die. When unfavorable conditions occur, mollusks secrete a dense film that closes the shell opening. Some can tolerate being out of the water for quite a long time.
Prudoviki, like other pulmonary gastropods, are hermaphrodites. Eggs and spermatozoa develop in the same organism, in different parts of the same gland, but after leaving it, the paths of the genital ducts are separated, and the male and female genital openings near the mouth of the shell open separately.
A muscular copulatory organ protrudes from the male genital pore during copulation, while the female genital pore leads to an extensive seminal receptacle. In pond snails, mating is observed, with one individual playing the role of a female and the other a male, or both mollusks mutually fertilize each other. Sometimes chains of copulating pond snails are formed, with the extreme individuals playing the role of a female or male, and the middle ones - both.
Egg laying continues throughout the warm season, from early spring, and in the aquarium in winter. The eggs of pond snails in the laid state are connected by a common mucous membrane. In an ordinary pond snail (Lymnaea stagnalis), the clutch looks like a transparent gelatinous sausage with rounded ends, which mollusks lay on aquatic plants or other objects (video). In this species, the length of the roller reaches 45-55 mm with a width of 7-8 mm; eggs in it 110-120.
Large pond snails are especially prolific. According to observations in the aquarium, one pair of pond snails produced 68 clutches in 15 months, and in the other, 168 clutches in 13 months. The number of eggs in a clutch varies by species.
After 20 days, tiny snails come out of the eggs, already equipped with a shell, which grow quite quickly, eating plant foods.
Representatives of some species of pond snails living in the deep lakes of Switzerland have adapted to live at great depths. Under these conditions, they are no longer able to rise to the surface to capture atmospheric air, their lung cavity is filled with water, and gas exchange occurs directly through it. This is possible only in clean, oxygen-rich water. Such mollusks, as a rule, are smaller than their counterparts living in shallow water.
- The shape of the common pond snail shell depends on the place of existence of a particular individual. These mollusks are extremely variable; not only their size, color, shape, but also the thickness of the shell vary.
- Shells of all European types of pond snails are twisted to the right. Only as an exception are individuals with left-handed (leotropic) shells.
- The number of eggs in a clutch, as well as the size of the egg cord, varies widely. Sometimes in one clutch you can count up to 275 eggs.
- A large pond is quite demanding on the oxygen regime. At high level oxygen saturation (10–12 mg/l), mollusk populations are characterized by a high population density. Very rarely, L. stagnalis was found in oxygen-deficient water bodies.
Interestingly, pond snails can breed far before reaching their maximum age and size. For example, an ordinary pond snail becomes sexually mature already at the end of the first year of its life, when it grows only to half its normal size.
- Pond snails can reproduce even being isolated from other individuals, so that copulation is not an act necessary for them to continue life, reproduction may well occur through self-fertilization.
- Pond snails are used in neurophysiology as model objects for studying the functioning of the nervous system of animals. The fact is that the nervous system of pond snails includes giant neurons. Placed in a nutrient medium, isolated pond snail neurons are able to stay alive for several weeks. The arrangement of giant neurons in the ganglia of the pond snail is fairly stable. This allows the identification of individual neurons and the study of their individual properties, which differ significantly from cell to cell. Irritation in the experiment of a single ganglion cell can cause a complex sequence of coordinated animal movements. This may indicate that giant mollusk neurons are capable of performing functions that in other animals are performed by large, complexly organized structures of many neurons.
- Snails have no hearing and voice, very poor eyesight, but their sense of smell is well developed - they are able to smell food at a distance of about two meters from themselves. The receptors are located on their horns.
- To improve digestion, the pond snail absorbs sand from the bottom of the reservoir
- Lifespan: 3-4 years.
- Maximum crawling speed - 20 cm/min.
- A large pond snail (L. stagnalis), when the reservoir dries up, releases a dense film that closes the shell opening. Some of the most adaptable forms of molluscs tolerate being out of water for quite a long time. So, an ordinary pond snail lives without water for up to two weeks.
- When water bodies freeze, mollusks do not die, freezing into ice, and come to life when thawed.
- Based on the results of recent joint research by scientists from the Pedagogical University of Tula and the Institute of Developmental Biology of the Russian Academy of Sciences, new, very Interesting Facts from the life of molluscs. As it turned out, snails have the ability to communicate with each other, transfer important information to each other, and even “give parental instructions” to larvae that have not yet been born, but are in the laid eggs. Although ordinary gastropod mollusks were chosen for the role of test subjects - a coil and a large pond snail, scientists have an assumption that absolutely all representatives use this method of communication. invertebrate world. At the first stage of the experiment, the experimental pond snails were divided into two groups. One of them was given food in the usual volumes, and the second was completely deprived of food for three days. Then water samples were taken from the containers in which the mollusks were kept, and from each container separately. As a result of the analysis, it was found that chemical composition differ significantly from each other. Then the caviar previously laid by the snails was placed in both containers. In the third, control container, caviar was also placed, but it was filled with clean water. All this was left for 10 days, after which the results were compared. As it turned out, in clean water, as well as in the one where well-fed snails lived, the larvae managed to reach the stage of full formation. The situation was completely different in the water where the hungry snails lived - the development of the larvae almost completely slowed down. This fact was commented on by Elena Voronezhskaya, Doctor of Biological Sciences, she said that parents seemed to warn their children not to rush to develop and hatch, as they would not have anything to eat. In the course of further experiments, the following pattern was discovered: the longer the fasting period of adult snails, the more they released into the water a special substance that inhibited the development of larvae. This substance has received the name "RED-factor" from scientists, according to their assumptions, it is a lipoprotein.
- At the pond most of liver is located in the last turns of the spiral.
- One of the forms of the pond snail has adapted to life in hot springs near Baikal - the elongated pond snail (Lymnaea peregra)
- Biologists drew attention to the large size and yellow-orange color of the nerve cells of the brain of a large pond snail, well adapted to a polluted environment. These cells are colored by pigments known as carotenoids. They can accumulate oxygen and, if it is not enough in the external environment, use the stored one.
- The blood of an ordinary pond snail is not red, like that of coils, but bluish, because it is colored with copper-containing hemocyanin.
While the news number for 07/25/18 was being made up. Scientists of the Federal Research Center for Comprehensive Study of the Arctic RAS (FICKIA RAS) and the Northern Arctic federal university(Arkhangelsk) created a genetic catalog of pond snails. For pond snails, their taxonomy was unclear, and we applied the molecular genetic method to Old World pond snails, examining material from about 40 countries. We conducted a revision, during which we showed that pond snails are divided into 10 genera, including a genus new to science and two species of pond snails discovered in remote high-mountainous regions of the Tibetan plateau. The genus is named Tibetoradix, and the species are Makhrov's pond snail (Radixmakhrovi) and the Tibetan Kozlov's pond snail (Tibetoradixkozlovi) in honor of the outstanding modern Russian ichthyologist Alexander Makhrov, as well as the traveler and explorer of the Central and East Asia Pyotr Kozlov, who lived in XIX-XX centuries.. It turned out that 35 species of pond snails live in Europe, Asia and Africa. "Before, grades ranged from three, ten or more"
And as usual, for those too lazy to read
In this article, we will consider who a pond snail is, what features it has, where it is found, and much more about this wonderful mollusk. What types of pond snails exist and what do they look like.
Any from pond snails, whether ordinary, small or large, is a snail that lives in ponds and gardens where there is enough moisture.
Large and small pond
The large pond snail belongs to the class of gastropods, which is the most numerous and diverse in comparison with other classes of gastropods. There are more than 90 thousand species of such mollusks in nature, and their habitat is not only ponds, but also the sea and land.
The large pond snail is about 5 cm long and has many distinctive features from the brothers.
Let's talk about the external structure of a large pond snail. It consists of three parts that are noticeable and perfectly distinguishable from each other. The body outside the shell is covered with a mantle to protect the internal mucosa, the shell of a mollusk is twisted for convenience in a spiral of 5 turns. This structure of the shell provides reliable protection of the body from irritants, mechanical damage. . The sink contains lime for the basis of the structure of spirals, and on top of it is covered with an organic substance of a horn-like type (such is on the horns of cattle, etc.).
Due to the structure of the shell, he received an asymmetric body for better accommodation in the "protection", the connection of the shell with the body is carried out due to the muscle. The muscle ensures that the animal is drawn into the shell, and with the help of a pronounced leg, the mollusk can crawl back.
In the internal structure pond snails of any type, everything is arranged simply. The main organs are:
- digestive complex;
- leg;
- eyes;
- excretory and respiratory system;
- sole and mucus secretion glands.
The snail feeds on plant foods in crushed form, then the food from the tongue (has a “grater”) passes into the throat, is processed by the secretion of splitting and processed in the stomach and intestines.
The circulatory system is open, and the molluscs move due to the powerful leg, which glides over any surface thanks to the secret secreted by the glands.
These animals are unique and do not need to be killed. . They don't harm a person, nor gardens, because they feed on plant foods that are easily processed (that is, weeds such as ephemera (wheatgrass, wood lice). Also, snails have healing properties, they proper nutrition and application secrete mucus that nourishes human skin and regenerates epithelial cells.
Small pond snail
Who are the puddlers in general, you know from the previous paragraphs, now we will talk about small things. In nature, there are several small pond snails:
Small snails are in all gardens, are small in size and beautiful appearance. Be supportive of snails, they do no harm, more good.
common pond snail
There is an ordinary pond snail in the middle lane - Russia, Europe. The pond snail has a large size, one shell is 7 cm, not including the body. The pond snail breathes with nothing more than miniature lungs, the circulatory system is not closed, they feed on hard plant foods, detritus and midges. The external structure does not differ from a large pond snail, except that the body does not always correspond to the size of the shell, sometimes smaller than the shell. Shell color - mother-of-pearl, brown. Body color - brown, gray, white.
Snails can easily survive both in nature and in the artificially created environment of a terrarium, aquarium. The snail moves thanks to the secretion of mucus and the outer sole, which allows it to move quickly enough over various distances. Snail mucus is rarely used in cosmetology, but most often the mollusk is kept for decoration.
Mollusks are attached to people - breeders, so if you fell in love with a snail, then do not give it to others, otherwise the weak heart of the animal will not stand it.
And now let's take a look at the photo of the pond
Snails big pond
The habitat of Lymnaea stagnalis is very extensive - bodies of water North Africa and North America, Asia, Europe.
The snail Prudovik Ordinary is able to live both in fast streams and in swamps, but it feels best in the coastal part of lakes. The pond snail actively crawls along the bottom of the reservoir and coastal vegetation, and sometimes goes out onto wet meadows.
The main difference between this one is that her eyes are at the base of the antennae.
The shell of the Prudovik has a brown color, which sometimes reaches dark. The base of the shell is rather fragile, the number of whorls varies within 4-5, the shell dimensions are up to 55 mm in height and up to 30 mm in width. Lymnaea stagnalis are able to move vertically (by secreting a path of mucus, they crawl along it in all directions).
Snails breathe atmospheric air with the help of a lung (a special section of the mantle cavity). To renew the air in the lung cavity, the mollusks rise to the surface of the water and breathe with the help of the edge of the mantle rolled into a tube.
In oxygen-rich water, pond snails are able to live at depth without rising to the surface. In this case, the lung is filled with water, through which gas exchange takes place.
The snail Prudovik feeds on both plant food and small insects and microorganisms. Quite often you can see snails eating the foliage of aquatic and coastal plants. If the number of molluscs in the reservoir increases greatly, then this is very harmful to the surrounding plants.
In an aquarium, Prudovik Ordinary can be fed with cabbage stalk, lettuce or raw potatoes.
Many freshwater inhabitants are not averse to eating this snail, as well as its caviar.
reproduction
By nature, Lymnaea stagnalis are hermaphrodites, so eggs are fertilized both by their sexual products and other snails.
at one time the snail lays a large number of eggs enclosed in transparent mucous masonry.
In an aquarium, reproduction of the pond snail is difficult, since most of the eggs laid are eaten.
The Prudovik snail reaches puberty when its shell grows up to 20mm in length.
The family of pond snails includes well-known and widely distributed throughout the world freshwater lung mollusks.
Of the large number of species belonging to this family, the common pond snail is best known for its large size, the largest specimens of which reach 7 centimeters. From early spring to late autumn you can observe these snails in ponds, in river backwaters, small lakes. It is interesting to watch how these bulky snails crawl on aquatic plants or along the bottom of a reservoir. There are especially many of them in the middle of summer among the floating leaves of egg capsules or water lilies.
Pond snails are omnivorous, therefore, crawling along the leaves and stems of aquatic plants, they scrape off radula algae from them, and at the same time they absorb small animals that they come across on their way. Prudovik is one of the most voracious inhabitants of fresh waters. It eats not only plants and animals, but also corpses.
You can often see how a pond snail, having risen to the surface of the water and hung to it from below with a wide sole of the foot, due to the surface tension of the water film, slowly and smoothly slides in this position. It is not in vain that pond snails rise to the surface of the water. Although they are aquatic organisms, but, like all pulmonary mollusks, they breathe with the help of a lung and are forced to rise to the surface in order to “sip” air. The respiratory opening of the pond snail, leading to the lung cavity, is wide open. The presence of lungs in pond snails indicates that these animals originated from land mollusks and have already returned to living in water for the second time.
Reproduction of pond snails
When mating, pond snails mutually fertilize each other, since, like all lung mollusks, they are bisexual creatures. Snail eggs are laid in the form of long, gelatinous, transparent cords, which are glued to various underwater objects. Sometimes eggs stick even to the shell of another individual of the same species. Pond eggs are a complex formation, since the egg cell is immersed in a mass of protein, and is covered with a double membrane on top. The eggs, in turn, are immersed in a slimy mass, which is dressed in a special capsule, or cocoon. A strand departs from the inner wall of the cocoon, attached at the other end to the outer shell of the egg, as a result of which it appears as if suspended from the wall of the cocoon. The complex structure of the egg clutch is also characteristic of other freshwater lung mollusks. Thanks to these devices, the egg is provided with nutritious material and protected by powerful shells. Inside these shells, the development of pond snails takes place without the stage of a free-swimming larva. It is likely that such protective adaptations of the eggs of pond snails were inherited from their land ancestors, where these adaptations were more important than when living in water.
The number of eggs in a clutch varies quite widely, as does the size of the entire clutch - the slimy cord. Sometimes you can count up to 270 eggs in one cocoon.
The pond snails are extremely variable, and the size of the mollusks, the shape of the shell and its thickness, and the color of the legs and body vary greatly. Along with large representatives, almost dwarf forms are known, undergrown due to unfavorable conditions and malnutrition. In some pond snails, the shell has thick, hard walls; there are also forms with an extremely thin and fragile shell that breaks at the slightest pressure. The shape of the mouth and whorl is highly variable. The color of the legs and body of the mollusc varies from blue-black to sandy-yellow.
This "tendency" to variability has played big role in the evolution of pond snails. Within the species, a large number of local varieties have arisen that differ in these characteristics, and it is often very difficult to determine whether this is a geographical subspecies or a variation due to specific habitat conditions in a given reservoir.
Types of pond snails
As well as common pond snail, a permanent inhabitant of our inland waters, there is another, also extremely variable species - an eared pond snail. In addition, ovoid pond snail, marsh pond snail and some others live in stagnant reservoirs.
Interestingly, pond snails living at considerable depths have been found in the deep lakes of Switzerland. At the same time, they are already deprived of the opportunity to rise to the surface to breathe air and have developed another adaptation. The lung cavity of these snails is filled with water, and they breathe oxygen dissolved in water. The absence of gills in pond snails, unlike primarily aquatic mollusks, again proves their origin from land snails.
Close to pond snails is the only representative of our fauna from the genus mixas, which differs from them in a very thin and fragile shell, almost completely covered with a mantle. Thus, the shell of this mollusk turned from the outer into the inner. These snails live mainly in floodplain ponds and lakes, where they sometimes breed in large numbers. However, in the middle of summer, snails disappear, as their life cycle ends in one season.
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