Large pond snail habitat. Common pond snail: description, nutrition, enemies and habitat

Many different snails live in ponds, rivers, and gardens, but the most common species is the pond snail. It lives in places where there is sufficient moisture, so it can be seen all over the world. This mollusk is quite often stocked in aquariums, as it copes remarkably well with plaque that forms on glass, stones or other objects, and it is also interesting to watch such a snail.

The pond fish does an excellent job of removing the deposits that form on the glass of the aquarium.

Description of the mollusk

The pond snail is a freshwater snail that has a well-developed spiral shell. The shell itself consists of five or six turns. On one side it has an mouth, and on the other there is a sharp peak. It reliably protects the soft body of the snail from various adverse effects and mechanical damage.

The pond fish breathes with the help of its lungs, and therefore it is forced to periodically rise to the surface of the water. At the very edge of the shell there is a special round hole that leads into the lung. And it is there that the blood is enriched with oxygen and carbon dioxide is released.

The pond snail's body consists of three main parts:

• heads;
• torso;
• legs.

The leg of a freshwater inhabitant occupies the abdominal part of the body. It is muscular, and with its help the snail moves along the surface. Life cycle in mollusks it is quite short, since in winter they all die. Depending on the species, pond snails differ from each other in the color of their shell, body and legs, and they may also have different shell shapes and thicknesses.

The most common types

Snails are unique animals that do not bring any harm to humans; on the contrary, they have many benefits, since they actively eat various weeds, clean the aquarium well of growth, and even have healing properties. In nature, there are many variants of the pond snail, each of which has its own characteristic features.

But the most common types are:

There are other types of these mollusks, but they are much less common. For example, there are pond snails that live at a depth of up to 250 m or at an altitude of 5 thousand meters.

Nutrition and reproduction

Feeds big pond snail mostly plant foods. In nature, it eats various weeds, algae and even rotten plants. In the aquarium, using a long tongue, it scrapes off the plaque that forms on the walls. This mollusk also eats any food that settles on the bottom.

As additional feeding, you can put small pieces of eggshells and chalk into the aquarium. From plant foods, snails can be given apples, cabbage, zucchini, pumpkin, carrots, and lettuce.

In nature, the pond snail eats various weeds, algae and even rotten plants.

Pond snails, like many other snails , are hermaphrodites, but their fertilization occurs in a cross way. They are also able to independently fertilize their own eggs. These moisture lovers put off the a large number of eggs, which are enclosed in a special transparent mucous clutch. Usually it has an elongated shape and is attached to various underwater objects, most often to vegetation. Sometimes one such clutch contains up to 300 eggs.

The eggs themselves are small and almost transparent. After about a month, small snails hatch from them, which external signs no different from adults. Pond fish reproduce quite actively, so if they are in an aquarium, you need to periodically remove excess eggs. In captivity, these mollusks can live up to two years, and during this period they lay eggs up to 500 times.

Difficulties in maintenance and illness

Pond fish are completely unpretentious animals, but the main difficulty in keeping them is that they can carry dangerous diseases, which at first glance are almost impossible to recognize. The most common disease in these mollusks is fungal infection. And if an infected individual is placed in a common aquarium with fish and other inhabitants, it can quickly spread the infection.

To avoid such a situation, before placing the pond snail in a community aquarium, you need to keep it in quarantine for several days. During this period, you should put it daily for several minutes in a weak solution of potassium permanganate or table salt.

If the snail does not consume the required amount of minerals and trace elements, then the walls of her shell may begin to become damaged or become thinner. In this case, the pond snail should be fed with foods that contain a high calcium content. After some time, the shell will heal and be completely restored.

Gastropods are the most numerous and diverse group of mollusks. It has about 90,000 species living in the seas, fresh water bodies, and on land. Most of them have a one-piece shell.

One of the representatives of this class lives in lakes, ponds and river backwaters - a large pond snail about 5 cm in size.

External structure

In the pond snail, all three parts of the body are clearly visible: the head, the leg and the bag-like body. The top of the body is covered with a mantle. The pond snail has a spiral shell, twisted in 4-5 turns, which protects the body of the animal. The shell is made of lime and is covered with a horn-like organic substance on top. Due to the spiral shape of the shell, the body of the pond snail is asymmetrical, 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 pulls the animal inside the shell.

The pond snail's leg is well developed, muscular, and has a wide sole. The animal moves slowly by sliding over plants or soil due to the wave-like contraction of the leg muscles. The copious mucus secreted by the skin glands of the leg facilitates smooth gliding.

Internal structure

Digestive system

In the mouth, on a special movable 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 in the pharynx salivary glands, the secretion of which processes food.

From the pharynx, food enters the stomach through the esophagus. The liver ducts flow into it. The stomach passes into the intestine, which makes several loops and ends with the anus at the anterior end of the body above the head.

Respiratory system

The body of the animal is covered on the outside with a mantle and is closely adjacent 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 not closed, 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 organs. A large vessel departs from the heart - the aorta. It branches into arteries. The blood then enters small cavities among the connective tissue. There the blood gives up oxygen, is saturated with carbon dioxide, enters the veins and travels through them to the lungs.

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 blood poor in oxygen and rich in carbon dioxide is called venous. The blood then collects 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, through a wide ciliated funnel, it communicates 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 mollusks is of the scattered-nodular type. It consists of five pairs of nerve ganglia (ganglia), interconnected by nerve bridges, and numerous nerves.

Due to the twisting of the body, the nerve bridges between some nodes form a cross.

Sense organs

The pond snail's head contains 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 located at the base of the tentacles. There are also organs of balance.

Reproduction. Development

Fertilization in the pond snail is internal. This animal is hermaphrodite. A single reproductive gland produces both sperm and eggs. They reproduce by eggs, which are laid on aquatic plants or other objects. Fertilized eggs are covered with a common mucous membrane and are securely attached to the substrate. Each animal lays about twenty clutches during the year.

After about twenty days, tiny animals emerge from the eggs. They grow quickly, eating plant foods.

The pond fish 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 live) dries out, not all mollusks die. Some secrete a dense film that closes the opening of the shell. In this state, a pond snail can live without water for about two weeks.

Family representative freshwater mollusks group of gray-eyed people. It has an elongated shell, strongly pointed towards the apex, curled to the right, usually thin and translucent. The shell curls expand very quickly and the last one, the so-called belly, occupies the most significant part of the shell. Its color is pale yellowish.
The pond snail, like the reel, is one of the mollusks with pulmonary respiration and therefore from time to time floats to the surface to inhale atmospheric air. Its body is greenish-dark gray in color with yellow spots. The head is equipped with two triangular flat tentacles, at the base on the outer side of which there are eyes. The leg is shorter than the reel leg, but significantly wider. From the leg, the body inside the shell rises upward in a spiral and forms, closer to the opening of the shell, a kind of sac that contains a mass of vessels and serves as a respiratory organ. On right side There is an opening for air inlet, which is closed by tightly locking muscles. The hole and the entire respiratory organ are easily visible when the animal, crawling along the plant, turns and often almost completely crawls out of the shell. This often happens when the pond snail, like a reel, crawls with its foot along the surface of the water, which it does in order to breathe atmospheric air.
Under the head there is a mouth opening, consisting of an upper jaw and two lateral sickle-shaped ones. A long tongue is also placed here, which scoops up algae. This is especially clearly visible when a pond snail crawls along the glass of an aquarium.
Pond snails are bisexual animals, and therefore they can be found mating 6-10 pieces together. Pond snails lay their eggs on the lower surface of floating leaves, on glass in an aquarium, and on various objects. The caviar is not connected in a flat cake shape, but in a worm-shaped or oval shape, similar to an icicle. From May to August they lay up to 20 such icicles, and each icicle contains 20-100 eggs. The eggs are transparent. The development of the embryo proceeds quickly, and after just a few days the embryo, covered with ciliated hairs, begins to rotate rapidly.
The snails hatch from their eggs no earlier than twenty, and sometimes even forty days, which, in all likelihood, depends on both the water temperature and the intensity of the lighting.
A remarkable phenomenon is sometimes observed with the gelatinous mass of eggs of these snails. It is covered with some kind of mold - small cilia with a pin-shaped thickening at the end, apparently, lily of the valley. These creatures apparently contribute to the destruction of this mass.
The snail reaches large sizes, and therefore is not entirely convenient for an aquarium. This inconvenience is increased by the fact that it grows so quickly and reaches large sizes in a short time.
Along with its rapid growth, this snail is distinguished by its gluttony, which preys on aquarium plants, with particular preference for plants that are at the same time soft and juicy. When young, the pond snail is not dangerous, since it is small and its appetite is insignificant.
Pond fish are capable of eating the corpses of their own brothers.
Also belongs to the same genus of pond snails Limnea stagnalis (common pond snail), even larger than the above.

Meet in Russia and Europe different types pond snails. Among them, the largest is the common pond snail, the shell of which can reach 7 centimeters. All species breathe through the lungs, therefore, from time to time they are forced to swim to the surface. You can often observe how the pond snail, a photo of which is presented in this article, smoothly and slowly slides along the lower part of the surface film of water, collecting oxygen from the air.

If the mollusks “suspended” in this way are somehow disturbed, they immediately release an air bubble from the breathing hole and fall like a stone to the bottom. The long-eared pond snail is the closest relative of the common pond snail. Its shell reaches 2.5 centimeters, which depends on the abundance of food and the temperature in its reservoir.

The common pond snail and other species of its family (in addition to those listed above, in our reservoirs you can find ovoid, small and marsh) are very variable. The shapes, sizes, thickness of the shell, and the color of the body and legs of the snails vary. Along with those that have a strong shell, there are species with very fragile, thin shell, which breaks even with the lightest pressure. There may also be various shapes helix and mouth. The color of the body and legs varies from sandy-yellow to blue-black.

Structure

The body of the mollusk is enclosed in a spirally twisted shell, which has an mouth and a sharp apex. The shell of the common pond snail is covered with a layer of lime, a horn-like greenish-brown substance. It is a reliable protection for his soft body.

In the body of a snail, 3 main parts can be distinguished: the leg, the head and the torso - although there are no sharp boundaries between them. Only the front part of the body, leg and head can protrude from the shell through the mouth. The leg is very muscular. It occupies the abdominal part. Such snails are called gastropods. At the same time, sliding along objects with the sole of the foot or hanging from the lower film of water, the mollusk smoothly moves forward.

The body copies the shape of the shell, fitting very closely to it. It is covered in the front part by a mantle (a special fold). The space between it and the body is called the mantle cavity. The body in front passes into the head, which has a mouth on the underside and two sensitive tentacles on the sides. Prudovik at light touch they instantly pull their leg and head into the shell. One eye is located near the base of the tentacles.

Circulation

The common pond pond has a rather interesting structure. So, he has a heart that pushes blood into the vessels. In this case, large vessels are divided into small ones. And from them blood flows into the spaces between the organs. Such a system is called “unclosed”. The interesting thing is that blood washes each of the organs. Then it is collected again into the vessels that lead to the lung, after which it goes directly to the heart. In such a system, it is much more difficult to ensure the movement of blood than in a closed one, since it slows down between organs.

Breath

Despite the fact that the snail lives in water, it breathes atmospheric air. To do this, the common pond snail, the structure of which is described in this article, floats to the surface of the reservoir and opens a round breathing hole at the edge of the shell. It leads to the lung - a special pocket of the mantle. The walls of the lung are densely braided. In this place, carbon dioxide is released and the blood is enriched with oxygen.

Nervous system

This mollusk has a circumpharyngeal concentration. From them, nerves extend to all organs.

Nutrition

The snail's mouth leads to the pharynx. There is a muscular tongue covered with teeth ─ the so-called grater. The common pond snail, a photo of which can be seen in this article, uses it to scrape off plaque from all kinds of microorganisms that form on various underwater objects, and also rubs various parts of plants. Food from the pharynx goes to the stomach, and then to the intestines. The liver also facilitates its digestion. The intestine opens through the anus into the mantle cavity.

Movements

If a caught pond snail is placed in a jar, it immediately begins to actively crawl along its walls. At the same time, a wide leg extends from the shell opening, which is used for crawling, as well as a head with two long tentacles. Sticking the sole of your foot to various subjects, the snail slides forward. In this case, gliding is achieved by wave-like, smooth muscle contractions, which can be easily observed through the glass of the vessel. It is interesting that the common pond snail can wander along the lower surface of the water, as we have already discussed above. In doing so, it leaves a thin ribbon of mucus. It stretches across the entire surface of the water. It is believed that snails moving in this way use fluids, hanging from below to an elastic film that forms on the surface due to this tension.

Such crawling can be easily observed on the calm surface of a reservoir while going on an excursion or relaxing in nature.

If a pond snail, crawling in this way, plunges into the water again under a little pressure, you will see how it rises to the surface again, like a cork. This phenomenon is easily explained: there is air inside the respiratory cavity. It supports the snail, just as the Prudovik can compress its respiratory cavity at will. In this case, the mollusk becomes heavier and therefore sinks to the very bottom. But when the cavity expands, it floats to the surface in a vertical line without any push.

Try immersing a pond snail floating on the surface of a pond and disturb its soft body with a touch of tweezers or a stick. The leg will immediately be pulled back into the shell and air bubbles will be released through the breathing hole. Next, the mollusk will fall to the bottom and will not be able to independently rise to the surface in any other way than by climbing onto plants, due to the loss of the air float.

Reproduction

The pond snail is a hermaphrodite, although it undergoes cross-fertilization. The snail lays eggs, which are enclosed in slimy transparent cords attached to algae. From the eggs emerge small pond snails with a very thin shell.

If you decide to keep a common pond snail, then you need to understand that a prerequisite for keeping it is a water temperature of about 22 ° C and its moderate hardness.

CLASS Gastropoda Molluscs (Gastropoda)

In gastropods, the body consists of a head, trunk and legs. The leg is the muscular abdominal part of the body, resting on which the mollusk slowly glides.

Most gastropods have a spirally twisted shell (which is why they are also called snails), into which the animal can completely hide. At the bottom of the shell there is a wide hole - the mouth, through which the mollusk sticks out its head and leg when moving. Some terrestrial gastropods - slugs - do not have shells.

In the pharynx of gastropods there is a muscular tongue covered with spines - the so-called grater. Using it, the mollusk scrapes out plant tissue or scrapes off plaque from various microorganisms that forms on underwater objects.

Family identification table

1(4) The mouth of the shell, when the mollusk draws its head and leg into it, is closed by a thin cap attached to the leg.
2(3) On the curls of the shell there are dark longitudinal stripes (may be difficult to see due to plaque covering the shell), up to 45 mm in size;
3(2) Shell without dark stripes, single color; size no more than 12 mm;
4(1) There is no lid at the mouth of the shell, so the compressed sole of the foot of the mollusk hidden in it is visible.
5(6) The coils of the shell are twisted in one plane;
6(5) The shell is twisted in a cone shape.
7(8) The shell is twisted to the right (if you take the shell so that the apex is directed away from you and the mouth towards you, then the mouth will be located to the right of the center line);
8(7) The shell is twisted to the left (the mouth is to the left of the center line); PRUDOVIKI FAMILY (Lymnaeidae)

In pond snails, the shell is twisted spirally, in several turns, in the form of a turret. About 20 species are found in the USSR.

Common pondweed (Lymnaea stagnalis) The largest of our pond snails, the shell height is 45-55 mm, and in some individuals even up to 65 mm. Inhabits stagnant bodies of water - ponds, lakes, river backwaters with abundant vegetation. Here you can see how the pond snail, sticking its leg and head with tentacles out of the shell, slowly slides along the plants. Having reached the surface of the water, the pond snail spreads its leg wider and slides, hanging from below to the surface film of the water. In this case, at the mouth of the shell, on the side of the leg, a round breathing hole can be seen. In mid-summer, the pond snail rises to the surface of the water 6-9 times within an hour. Distributed in Europe and North Asia to Kamchatka.

Pond snail (Lymnaea auricularia) This mollusk has a shell with a very wide mouth, shell height 25-40 mm, width 20-30 mm. Lives in the surf zone of standing water bodies. Distributed in Europe and Asia (except the southeast).

COIL FAMILY (Plarmrbidae)

In coils, the shell turns are located in the same plane. The coils are not as mobile as pond snails and cannot be suspended from the surface film of water. There are 35 types of reels found in the USSR.

Horn coil (Planorbarius corneus) This mollusk has a shell diameter of up to 35 mm. It lives on plants in stagnant bodies of water, in the same place as the common pond snail, but rarely rises to the surface of the water. Distributed in Europe and Western Siberia to the Ob.

Coil edged (Ptanorbis planorbis) The edged coil has a dark brown shell, 20 mm in diameter, with 5-6 turns. On the last whorl below there is a sharp protrusion - the keel. Inhabits small reservoirs and the coastal parts of large reservoirs. Distributed in Europe and Western Siberia to the Yenisei.

Coil twisted (Anisus vortex) The shell is yellow, up to 10 mm in diameter, with 6-7 whorls. On the last whorl there is a sharp, downwardly displaced keel. It lives in coastal thickets of stagnant bodies of water and often floats on the surface of the water. Distributed in Europe and Western Siberia to the Yenisei.

PHYSIS FAMILY (Physidae)

Physids have a tower-shaped shell, like those of pond snails, but twisted to the left.

Physa vesicularis (Physa fontinalis) The shell is matte, pale yellow, 10-12 mm high, 5-6 mm wide, the height of the mouth is more than half the height of the shell. Inhabits vegetation in various permanent bodies of water. Distributed in Europe and Northern Asia.

Aplexa sleepy (Aptexa hypnorum) The shell is shiny, golden brown, 10-15 mm high, 5-6 mm wide (the height of the mouth is less than half the height of the shell). Lives only in temporary bodies of water that dry up in summer. Distributed in Europe, Western Siberia and the south of the Far East.

LUZHANKA FAMILY (Viviparidae)

The mouth of the shell is closed by an operculum at rest. Shells with dark longitudinal stripes. Meadow mollusks are also called livebearers, since they do not lay eggs like other mollusks, but give birth to small meadows that already have a shell.

Swamp meadow (Viviparus contectus) Sink up to 43 mm high. It lives in lakes, ponds, and sometimes even in puddles of clean water. Stays on the bottom. Distributed in Europe and Western Siberia to the Ob.

BITINI FAMILY (Bithyniidae)

Like the lawns, the mouth of the shell is closed by an operculum when at rest, but the shells are single-colored, without stripes.

Bitinia tentacular (Bithynia tentaculata) Sink up to 12 mm high. Inhabits stagnant and weakly flowing water bodies, on rocks, in silt and among plants. Distributed in Europe and Western Siberia.

Terrestrial gastropods

Terrestrial gastropods can be divided into two groups: snails, which have a shell, and slugs, which do not have a shell (in some species, a small remnant of the shell is hidden under the skin and is not visible from the outside). Since mollusks have bare skin, many species stick to wet habitats. In addition, during the day the animals are usually motionless. In this case, the snails completely hide in the shell, sucking the sole of their feet to the substrate, and the slugs crawl under shelters - stones, leaves, between lumps of soil. But at night, and in rainy times and during the day, the mollusks crawl from place to place.

SNAILS

In land snails, the shell is twisted in a spiral. In some species the shell is elongated, so that its height is noticeably greater than its width; in other species, on the contrary, the shell is low and its width is greater than its height. While moving, the mollusk sticks its head and leg out of the shell. There are 4 forward-facing tentacles visible on the head. At the ends of the two longer tentacles there are dark balls - these are eyes. If you carefully touch the tentacles, the mollusk immediately retracts them, and if it is greatly disturbed, it will completely hide in the shell. Several hundred species of snails are found in the USSR. Basically, these are very small species that are difficult to distinguish from each other (often only by internal structure). We will consider only some of the largest and most widespread forms.

Common Yantarka (Succinea putris) It got its name from the amber-yellow color of its elongated, thin, fragile, almost transparent shell. Shell height 16-22 mm, width 8-11 mm. Shell with 3-4 whorls, the last whorl is strongly swollen and widened, the aperture is ovoid. The amberfish lives in damp places - in wet meadows, near bodies of water, it can often be seen on the floating leaves of aquatic plants, and sometimes it even submerges in water. Widely distributed throughout the USSR.

Cohlicopa is slippery (Cochticopa lubrica) This is a small snail, with a smooth, shiny, elongated, conical shell, 6-7 mm high, 3 mm wide. It is very common in damp places - in meadows, grass, moss, and fallen leaves of damp forests. Distributed throughout the USSR.

Iphigena swollen (Iphigena ventricosa) This snail has an elongated, fusiform, ribbed, reddish-horned shell, 17-18 mm high, 4-4.5 mm wide, with 11-12 whorls. A flat tooth-like protrusion protrudes into the mouth from above. Lives in forests, on litter, on mossy tree trunks. Distributed in the Baltic states and the central zone of the European part of the USSR.

Cochlodina rocky (Cochlodina laminata) This species has an elongated, fusiform, slightly swollen, smooth, shiny, light-horned shell, 15-17 mm high, 4 mm wide, with 10-12 whorls. Two lamellar curved protrusions are visible at the mouth. Lives in forests, on rocks, stumps, tree trunks. Distributed in the central zone of the European part of the USSR, north to Leningrad region, east to Kazan.

Bush snail (Bradybaena fruticum) This snail has a spherical shell, almost smooth, 16-17 mm high, 18-20 mm wide, with 5-6 whorls. The color can vary from grayish-white to reddish-horny, often with a narrow brown stripe visible on the last whorl of the shell. It lives in bushes, deciduous forests, gardens; the bush snail can often be found on nettles and coltsfoot. Sometimes she climbs quite high on bushes, tree trunks and fences. Distributed in the European part of the USSR, Crimea and the North Caucasus.

Garden snail (Cepaea hortensis) U garden snail the shell is cube-shaped, similar to the shell of a bush snail, 15-16 mm high, 19-21 mm wide, with 4-5 whorls, dark spiral stripes are visible on all whorls. Lives in sparse bushes and forests, on stones and cliffs. Distributed in the Baltic states

Hairy snail (Trichia hispida) This small snail has a shell covered with fine hairs (in older specimens they may be erased). The shell is 5 mm high, 8-9 mm wide, grayish or reddish-brown in color, usually with a light stripe on the last whorl. It lives in bushes, on the ground in the forest floor, under stones, and dead wood. Distributed in the forest zone of the European part of the USSR, up to Leningrad and Perm regions. It often causes damage to garden crops, fruit and berry crops and ornamental plants, scraping out leaf tissue so that only thick longitudinal veins remain.

SLUGS

Slugs have a naked body, without a shell. In a calm state, slugs look like small mucous lumps, but when they move, their body stretches greatly. Like snails, 4 tentacles pointing forward are visible on the head. There are eyes at the ends of the two longer tentacles. A short neck is visible behind the head, extending into the back. Immediately behind the neck, an oval thickening is visible on the back, as if another layer of skin was placed on top. This is the so-called mantle, covering the respiratory organ - the lung. A rounded respiratory opening is visible on the right side of the mantle. As the name suggests, slugs produce a lot of mucus. It primarily protects the shellfish from drying out. In addition, mucus helps them when sliding. A crawling slug always leaves a noticeable shiny slimy trail. In the central zone of the European part of the USSR there are 16 species of slugs. Of these, we will consider the most common, widespread forms.

Determinative table of childbirth

1(2) The respiratory opening is located in the front part of the right edge of the mantle. When moving, the end of the leg protrudes slightly from under the back;
2(1) The breathing hole is located at the back of the right edge of the mantle. The leg does not protrude from under the back when moving.
3(4) Large slugs, over 100 mm long.
4(3) The size of slugs does not exceed 50 mm.
5(6) Slime yellow;
6(5) The mucus is colorless, and when the mollusk is irritated, it becomes milky white; KIND OF ARION (Arion)

The body is thick and massive. The mantle is oval, rounded at the front and back. Breathing hole in the front part of the right edge of the mantle. When moving, the end of the leg protrudes slightly from under the back.

Arion brown (Arion subfuscus) Body length up to 80 mm. The mantle is about 1/3 of the body length. The color can vary, from brown to orange, most often rusty. The middle of the back is usually darker. Lives in deciduous, mixed and coniferous forests, occasionally found in old parks and cemeteries. Favorite food is cap mushrooms, in which the slug eats out large cavities. It can also feed on dead parts of plants and animal corpses. Distributed in forest and forest-steppe zone European part of the USSR. In the Altai region, Eastern Siberia, the Amur basin and the Primorsky Territory live the subspecies Arion brown Siberian (Arion subfuscus sib ire us), characterized by a monochromatic black body color. In warm, damp summers, this slug causes damage to vegetable gardens and fields located near the forest.

Arion striped (Arion fasciatus) Body length up to 50 mm. The mantle occupies about 1/3 of the body length. The color is light - cream or yellowish-ashy, the middle of the back and mantle is slightly darker. There are clearly demarcated dark stripes on the sides. It is found more often in cultural biotopes - vegetable gardens, fields, orchards, parks. Often causes significant damage to agricultural crops. Distributed in the northwestern and central regions of the European part of the USSR.

GENUS DEROCERAS (Deroceras)

Small slugs, quite slender and mobile. The skin is almost smooth, with faint grooves, without rough wrinkles. Breathing hole at the back of the right edge of the mantle. The mucus is colorless, and when the mollusk is irritated it is milky white.

Reticulated slug (Deroceras reticulatum) Body length 25-35 mm. The mantle occupies about half the length of the body. The coloring is mostly cream or light coffee, with dark spots forming a grid-like pattern, especially noticeable on the mantle and back. The head and neck are also covered with small spots; tentacles are blackish. Lives on open places, avoiding forests and shrubs, more often on clay soils - meadows, fields, vegetable gardens, landfills, and in cities - in parks and gardens. Of all the slugs, the most dangerous pest agricultural crops. In vegetable gardens, it readily attacks cabbage, eating large holes not only in the outer leaves, but also inside the head of cabbage. In rainy years it damages winter crop seedlings. Widely distributed in the European part of the USSR.

Field slug (Deroceras agreste) Body length 35-40 mm. The mantle occupies about 1/3 of the body length. The color ranges from almost white to cream, without a dark pattern. It lives in open places - meadows, swamps, near roadside ditches, on forest edges, but, unlike the netted slug, it avoids places with cultivated soil. Widely distributed throughout the USSR.

Slug smooth (Deroceras laeve) Body length up to 25 mm. The mantle occupies about half the length of the body. Color ranges from reddish-brown to almost black, monochromatic. Very moisture-loving and cold-resistant. It lives in swamps, wet meadows, damp forests, on the banks of small overgrown reservoirs - here it can be found not only on soil and plants, but also on their underwater parts. Widely distributed throughout the USSR.

GENUS LIMAX (Limax)

Large slugs, more than 100 mm long. The color is spotty, sometimes the spots merge into dark stripes. A keel protrudes on the caudal part of the back. The body is wrinkled, the wrinkles are long, convex, with deep grooves between them.

Slug black (Limax cinereoniger) Body length 150-200 mm. The mantle occupies about 1/4 of the body length. The color is black or dark gray, the keel is light. Tentacles with black dots. Lives in deciduous and mixed forests, can also live in coniferous forests with good grass cover. It feeds mainly on mushrooms and lichens. Distributed in the Karelian Autonomous Soviet Socialist Republic, the Baltic states, Belarus, in the western and central regions of the RSFSR, east to Nizhny Novgorod.

Large slug (Limax maximus) Body length up to 130 mm. The mantle occupies about 1/3 of the body length. The color is variegated: on a yellowish, ash-gray or dirty white background there are 2-3 pairs of dark stripes or rows of dark spots. The tentacles are single-colored, without dark spots. It lives in cities - in parks, gardens, greenhouses, vegetable stores, where it can cause harm. Distributed in the northwestern and central regions of the European part of the USSR.

GENUS MALACOLIMAX (Malacotimax)

Malakolimax gentle (Matacolimax tenellus) Body length up to 50 mm. The mantle occupies about 1/3 of the body length. The color is one-color, often yellow, greenish or grayish-yellow, sometimes orange-yellow. The head and tentacles are black or dark brown. The mucus is yellow. Lives in deciduous forests, occasionally in coniferous ones. Feeds cap mushrooms and lichens. Distributed in the northwestern, western and central regions of the European part of the USSR.

CLASS BIVALVE MOLLUSCS (Bivalvia)

In bivalves, the shell consists of two halves connected on the dorsal side by an elastic ligament. On the ventral side, the halves of the shell can move slightly apart, and the leg of the mollusk protrudes through the resulting gap. When moving, the mollusk pushes the silt or sand at the bottom with its foot, like a plow, hooks its foot into the ground and pulls the body with the shell forward, again pushes the leg forward, pulls itself up again and thus crawls along the bottom in small steps. Some bivalves do not move, but sit in one place, attached to the substrate with special adhesive threads. Bivalve mollusks do not have a head, so they do not have a grater. They feed on small planktonic organisms, which are sucked in along with water through a siphon opening located at the rear end of the body. All bivalves live in water.

Dreissena river (Dreissena polymorpha) The shell of the river dreissena is greenish-yellow, with brown stripes, length 30-50 mm. The lower edge adjacent to the place of attachment is flat, the two lateral edges are convex. Lives in rivers, lakes and reservoirs.

PERLOVITSA FAMILY (Unionidae)

Pearl barley has an elongated oval shell. On each valve, the most convex, protruding part is visible - the apex. Concentrating around the apex, arched lines run along each valve. Some of these arcs are sharper, darker - these are annual arcs, from which you can approximately determine the age of the mollusk. There are 4 genera in the family. The most famous are pearl barley and toothless.

GENUS OF PERLOVITSA (Unio) Pearl barley has a thick-walled shell, the tops of the valves protrude upward. If you look at the shell from the end, the place where the valves are held together - the ligament - will be in the recess.

Common pearl barley (Unio pktorum) The common pearl barley has a long, narrow shell, up to 145 mm, with almost parallel dorsal and ventral edges. The color of young individuals is yellow-green, and that of older ones is greenish-brown. It lives in lakes and rivers, in places with slow flows, on sandy, not very silted soil. Distributed in the European part of the USSR, except in the north and northeast.

Pearl barley swollen (Unio tumidus) This species has a shorter shell, up to 110 mm, with non-parallel edges. The habitats and distribution are the same as those of the common pearl barley.

GENUS OF TOOTHLESS (Anadonta) Toothless shells have a thin-walled shell, the tops of the valves do not protrude much. If you look at the sink from the end, the place where the valves are fastened is not deepened. Some species have a large keel on the upper edge of the valve. The shape of the shell is very variable among individuals of the same species living in different bodies of water.

GENUS OF PEA (Pisidium) In peas, the top of the shell valves is shifted to the side, the shell is short-oval. The size of the peas does not exceed 11 mm.

River pea (Pisidium amnicum) The diameter of the river pea shell is 10-11 mm. It lives in river backwaters and lakes, on silt-sandy soil. Distributed in the European part of the USSR and in Siberia to the Lena.