Self-development 

A large pond snail breathes with help. Big pond snail. Habits in the wild and life expectancy

After starting a new aquarium, novice aquarists are often faced with the problem of contamination and the appearance of unwanted algae. There are many ways to clean an aquarium tank, the best of which, perhaps, is biological, that is, adding natural cleaners to the fish. Often, fish owners resort to the help of pond snails. They not only help fight pollution, but are also interesting in terms of observing their behavior.

Description, types

The pond snail (lat. Lymnaeidae) is a snail belonging to the genus of pulmonate mollusks. As the name implies, it lives in fresh water bodies with stagnant water or water with a very slow flow.

Did you know? Snails belong to the most ancient animals on Earth. According to scientists, they appeared over 500 million years ago.

The body of the mollusk is divided into three parts: head, torso and leg. The pond snail has a finely spiraled shell with five to six whorls, mostly twisted to the right. Left-handed ones are found among the inhabitants of New Zealand and the Sandwich Islands. The shell opening is large, rounded at the front. The shape of the shell depends on the current of the body of water where the snail lives. Its dimensions range from 1 to 6 cm in height and from 0.3 to 3.5 cm in width. The body is tightly attached to the shell.
The head of this mollusk is large. It has flat, triangular-shaped tentacles with eyes on their inner edge. The hole through which the pond snail breathes is protected in the form of a prominent blade. The color of the snail depends on the living conditions. The shell is usually brown. The head and body can be colored from black with a blue tint to yellow with brownish. In nature, the pond snail is represented by many species living in the Northern Hemisphere, in Eurasia,, North Africa North America

Did you know?. Some of its representatives can be found in geysers, sulfurous, slightly salty and salty waters. They can be found even at an altitude of 5.5 thousand meters in Tibet and at a depth of 250 m. The snail's tiny brain is divided into four sections and is quite efficient. Scientists claim that these mollusks have the ability to take. After conducting more detailed studies of two neurons that are responsible for the feeling of hunger and the decision to go for food, they decided to use this data to work with simple algorithms in robotics.

Each species is distinguished by the characteristic color of the shell, body, leg, as well as the shape and thickness of the shell walls, the shape of the helix and the mouth.

We invite you to take a closer look at the most famous species:

  1. The common prudovik is a big one. The largest in our area and the most famous representative families. The shell is elongated, conical, 4.5-6 cm long and 2-3.5 cm wide. It is twisted in a spiral with 4-5 turns, which quickly expand, forming a large hole. Its color is brown, the walls are thin and translucent; The body of the mollusk is greenish-gray. The species is widespread, found throughout Northern Hemisphere in various freshwater bodies.
  2. This species has an elongated, pointed at the top and durable shell. The curls twist to the right and have six to seven turns. The shell is thin, almost transparent, pale yellow color. Its dimensions are small: length - 1-1.2 cm, width - 0.3-0.5 cm. The body and mantle of this pond snail are light gray. There are dark spots on the mantle. The species is distributed throughout Russia, living in ponds, swamps, and puddles. Can live along the banks of drying up reservoirs.
  3. Ushkovy. It is named so because the mouth of the shell is very similar in appearance to a human ear. Its shell is small - 2.5-3.5 cm in height and 2.5 cm in width. Has thin walls. Painted in a gray-yellow tint. Has up to four turns. The last turn is very large. The body is colored green-gray or yellow-green with numerous inclusions. The mantle can be plain - light gray, or spotted. The eared pond snail lives in various reservoirs, lives on plants, snags, and stones.
  4. Ovoid or oval. Like the eared pond snail, the egg-shaped shell curl makes up a third of the mouth. The sink has thin walls and is therefore very fragile. U adult it is 2-2.7 cm in height and 1.4-1.5 cm in width. The shape of the mouth is ovoid. The shell is painted light pink, shiny and almost transparent. The body is light gray or light olive in color. The mantle is also light gray. The natural habitat of the egg-shaped pond snail is lakes and quiet rivers. It can live both in the coastal zone and in the depths.
  5. The marsh pond snail has a shell height of 3.2 cm and a width of 1 cm. In appearance, this species is similar to the common pond snail, but differs from it in that its shell has the shape of a sharp cone with a small hole. It is dark brown in color. In addition, the marsh one is smaller than usual: the height of the shell is 2-3 cm, the width is 1 cm. There are six to seven whorls on the shell. Its walls are thick. The body is greenish-gray in color. The mantle is light. Lives in small bodies of water - swamps, puddles, streams, ponds.
  6. Frilled or frilled. It got its name due to the fact that its shell is completely or partially covered by a mantle. The shell of the raincoat is shiny and smooth. It can be colorless, yellowish or yellowish-horny. It is small in size, its height is 1.9 cm, width is 1.2 cm. It has 2.5-4.5 curls. The last one is very big. The shape of the shell resembles a ball. The mouth is oval and large. The body is colored olive and gray with numerous inclusions. The mantle is yellow-brown or yellow-green with large light spots. Lives in lakes quiet rivers, in shallow water.

Habitat in nature

In nature, common pond snails eat mainly plants. However, their diet may also include animal food (flies, fish eggs, etc.) and bacteria. They breathe as they crawl out of the water to the surface. They need to carry out six to nine such lifts per day. Those snails that live at great depths are able to subsist on air dissolved in water. They draw water into the pulmonary cavity. Pond snails can swim - they turn their soles up and give it a slightly concave shape.

Did you know? Snails have no hearing or 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. Receptors are located on their horns.

Under natural conditions, these snails can rarely be found idle; usually they are “in a hurry” somewhere, busy with something - for example, scraping algae from stones. Maximum speed which they can develop is 20 cm per minute.
It is interesting that these mollusks are able to survive when the reservoir dries out, sealing the shell with a thick film, as well as when the pond is covered with ice - after it thaws, they come to life and continue their life activities. average life expectancy aquarium pond snail- two years, in the wild - nine months.

The pond fish is an unpretentious aquarium inhabitant. The main conditions for its maintenance are the water temperature not lower than 22°C, its moderate hardness and weak light - preferably fluorescent with minimal power.
With warmer water, snails will reproduce more often and actively, and this is not desirable for home aquariums. The size of the aquarium is not important. Rocky soil is suitable. It can be pebbles or coarse sand.

No special cleaning is required for shellfish. All you need is standard procedures that every aquarist should follow:

  • weekly water change by 30%;
  • aeration;
  • filtration.

Nutrition, mineral supplements

Every aquarium owner planning to place a pond snail in it will be interested in the question of what it eats and where to get food for it. There will be no problems with this, since he can eat what the fish haven’t eaten, their excrement, and rotten plants. A person can prepare a salad for him from finely chopped greens, cabbage, zucchini, pumpkin, tomatoes, and other vegetables and fruits.
You should be careful when introducing pond snails into an aquarium, since upon reaching adulthood they can be very voracious and eat most of the underwater vegetation. Occasionally, snails will need to be fed with mineral supplements. The main thing for them is calcium, so you can add crushed eggshells, chalk, sepia.

Important! You should not plant pond snails in a tank where soft and succulent underwater plants grow. This threatens the death of the latter. These snails cannot handle only algae with hard, dense leaves.

Compatibility with other aquarium inhabitants

Diseases

Snails rarely get sick. But they themselves serve as a source of infectious diseases for other aquarium inhabitants. Moreover, the danger lies in the fact that usually the presence of infection in the body of a mollusk does not affect its appearance, so it is not always possible to immediately determine whether it is dangerous for fish or not. The most common disease in the small pond snail is fungal infection - its shell becomes covered with a white coating.
Treatment will consist of baths with the addition of solutions of salt or potassium permanganate. Also, if a clam does not consume the required amount of vitamins and minerals, the walls of its shell may become thin and damaged. If you observe this problem, it is worth feeding the snail with substances containing calcium. Small cracks will disappear on their own after some time after starting treatment. But the deep ones will need to be “glued together” with a special preparation sold in zoological stores.

Breeding

Pond snails reach sexual maturity at six to eight months. Since they have no sexual differences, representatives of the pond snail family reproduce by laying eggs, usually from 20 to 130 per clutch. This process can occur in them several times a year, and over the course of its entire life, one individual is capable of producing offspring about five hundred times. Mollusks lay eggs on the leaves of plants. Incubation occurs within 14-20 days. The eggs hatch into babies with a thin shell. Thus, pond snails, in addition to being very voracious, are also fertile. Therefore, aquarists do not have a question about breeding them. More often, another problem arises - how to prevent their frequent reproduction and overpopulation of the aquarium. If the task is to breed these mollusks, then the reproduction process can be stimulated by raising the water temperature by a couple of degrees.

Did you know? The biggest sea ​​snail They consider the giant Australian trumpeter, whose shell reaches 91 cm and weighs 18 kg. The tiger Achatina is recognized as the largest land mollusk - with a shell 27.5 cm high and a body weight of about 1 kg.

It is not necessary to add snails to the aquarium yourself. They can appear unexpectedly - their eggs are carried along with underwater plants. In this case, the owner needs to organize their proper maintenance and ensure that the number of individuals does not exceed the capabilities of the aquarium tank. If it is possible to control their reproduction, then the presence of pond snails will definitely benefit the fish’s home - they can help get rid of unfriendly algae settling on the decor, walls and plants, and keep their place of residence clean. Mollusks are indispensable cleaners for spawning aquariums. An overpopulation of snails threatens oxygen deficiency, which is why, first of all, the fish will suffer. Thus, it is possible, but not advisable, to keep pond snails in an aquarium. On the one hand, they are able to clean the tank and get into places where they cannot reach human hand, get rid of unnecessary algae. In addition, they do not require special care and nutrition. On the other hand, these snails can cause serious damage to underwater plants and, as a result, to the beauty of the aquarium. They are often added to an aquarium without live algae by beginners. Experienced aquarists prefer to deal with snails of other species.

Molluscs, or soft-bodied mollusks, live in the sea, in fresh waters and on land. The body of mollusks is usually covered with a shell, under which there is a fold of skin - the mantle. The space between the organs is filled with parenchyma. About 100,000 species of mollusks are known. We will get acquainted with representatives of three classes: gastropods, bivalves and cephalopods.

Lifestyle and external structure. In ponds, lakes and quiet river backwaters, you can always find a large snail on aquatic plants - the large pond snail. On the outside, the pond snail's body is covered with a protective spirally twisted shell about 4 cm long. The shell consists of lime, covered with a layer of greenish-brown horn-like organic matter. The shell has a sharp apex, 4-5 whorls and a large opening - the mouth.

The pond snail's body consists of three main parts: head, torso and legs. Only the leg and head of the animal can protrude from the shell through the mouth. The pond snail's leg is muscular. When wave-like muscle contractions run along its sole, the mollusk moves. The pond snail's leg is located on the ventral side of the body, and therefore it is classified as a gastropod. In front, the body meets the head. A mouth is placed on the underside of the head, and two tentacles are located on its sides. The pond snail's tentacles are very sensitive: when you touch them, the mollusk quickly retracts its head and leg into the shell. There is an eye near the base of the tentacles on the head.

The body follows the shape of the shell, closely adhering to its inner surface. The outside of the body is covered with a mantle, with muscles and parenchyma located underneath it. Inside the body there remains a small cavity in which the internal organs are located.

Nutrition. The pond fish feeds on aquatic plants. In his mouth is a muscular tongue covered with hard teeth. The pond fish from time to time sticks out its tongue and scrapes off the soft parts of plants with it, like a grater, which it swallows. Through the pharynx and esophagus, food enters the stomach and then into the intestines. The intestine bends in a loop inside the body and ends on its right side, near the edge of the mantle, with the anus. Next to the stomach in the body cavity lies a greyish-brown organ - the liver. Liver cells produce digestive juice, which flows through a special duct into the stomach. Thus, digestive system The pond snail is even more complex than that of the earthworm.

Breath. Despite the fact that the pond snail lives in water, it breathes oxygen from atmospheric air. To breathe, it rises to the surface of the water and opens a round breathing hole on the right side of the body at the edge of the shell. It leads to a special pocket of the mantle - the lung. The walls of the lung are densely intertwined with blood vessels. This is where the blood is enriched with oxygen and carbon dioxide is released. Within an hour, the mollusk rises to breathe 7-9 times.

Circulation. Next to the lung is the muscular heart, consisting of two chambers - the atrium and the ventricle. Their walls alternately contract (20-30 times per minute), pushing blood into the vessels. Large vessels turn into thin capillaries, from which blood flows into the space between the organs. Thus, circulatory system unclosed mollusk. The blood is then collected in a vessel that approaches the lung. Here it is enriched with oxygen and flows through the vessel into the atrium, and from there into the ventricle. Pond snail blood is colorless.

Selection. The pond snail has only one excretory organ - the kidney. Its structure is quite complex, but general outline resembles the structure of the excretory organs of an earthworm.

Nervous system. Main part nervous system The pond snail is a peripharyngeal cluster of nerve ganglia. Nerves extend from them to all organs of the mollusk.

Reproduction. Pond fish are hermaphrodites. They lay masses of eggs encased in transparent slimy cords that attach to underwater plants. The eggs hatch into small mollusks with a thin shell.

Other gastropods. Among large number species gastropods The marine ones are especially famous for their beautiful shells. Slugs live on land, so called because of the abundant mucus they secrete. They don't have shells. Slugs live in damp places and feed on plants. Many slugs eat mushrooms, some are found in fields and gardens, causing damage to cultivated plants.

Widely known grape snail, which is used as food in some countries.

Big pond snail - inhabitant of fresh water bodies. It has a cone-shaped, spirally twisted shell with 4-5 curls, a sharp apex and a large opening - the mouth. The shell serves as protection for the soft parts of the mollusk’s body; muscles are attached to it from the inside. The shell consists of lime covered with a layer of greenish-brown horn-like substance. In body pond snail three main parts can be distinguished: torso, head and leg, but there are no sharp boundaries between them. Through the mouth, the front part of the body and the leg protrude out. leg pond snail muscular. When wave-like muscle contractions run along its sole, the mollusk moves. Leg pond snail located on the ventral side of the body (hence the name of the class - gastropods).

The body follows the shape of the shell, closely adhering to its inner surface. On the outside it is covered with a fold of skin - the mantle. In front, the body meets the head. A mouth is placed on the underside of the head, and two sensitive tentacles are located on its sides. When touched, the mollusk quickly pulls its head and leg into the shell. There are eyes near the base of the tentacles on the head.

    Features of life processes: Prudovik feeds on aquatic plants. In his throat is a muscular tongue covered with hard teeth. Prudovik From time to time it sticks out its tongue and scrapes it, like a grater, with the soft parts of plants, which it swallows. Through the pharynx and esophagus, food enters the stomach and then into the intestines. The intestine bends in a loop inside the body and ends near the edge of the mantle with the anus. Unlike all previously studied animals at pond snail There is digestive gland the liver, the cells of which produce digestive juice. Thus, the digestive system pond snail more difficult than that of an earthworm.

    Breathing is pulmonary. Periodically rising to the surface of the water, it fills the mantle cavity with fresh air through a round breathing hole. The walls of the lung are densely intertwined with blood vessels; here the blood is enriched with oxygen and carbon dioxide is released. Within an hour, the mollusk rises to breathe 7-9 times. Next to the lung is the muscular heart, consisting of two chambers - the atrium and the ventricle. Their walls alternately contract (20-30 times per minute), pushing blood into the vessels. Large vessels turn into thin capillaries, from which blood flows into the space between the organs. Thus, unlike annelids, the mollusk’s circulatory system is not closed, since it communicates with the body cavity and blood does not flow through the vessels all the time. From the body cavity, blood collects in a vessel that approaches the lung, is enriched with oxygen and enters the atrium. Blood pond snail colorless. The excretory organs are represented by one kidney. Main part of the nervous system pond snail constitutes a peripharyngeal cluster of nerve ganglia. Nerves extend from them to all organs of the mollusk.

    Reproduction: Hermaphrodite. Postpones a large number of eggs enclosed in transparent mucous cords. Which are attached to underwater plants. The eggs hatch into small mollusks with a thin shell.

The habitat of Lymnaea stagnalis is very extensive - water bodies of North Africa and North America, Asia, and Europe.

The Common Prudovik snail 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 comes out onto wet meadows.

The main difference between this one is that its eyes are located at the base of the antennae.

The Prudovik shell has Brown color, which sometimes goes dark. The base of the shell is quite fragile, the number of curls varies between 4-5, the dimensions of the shell are up to 55mm in height and up to 30mm in width. Lymnaea stagnalis are able to move vertically (by secreting a path of mucus, they crawl along it in all directions).

Snails breathing atmospheric air using the lung (a special part of the mantle cavity). To renew the air in the pulmonary cavity, the mollusks rise to the surface of the water and breathe using the edge of the mantle rolled into a tube.

In water rich in oxygen, 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 occurs.

The Prudovik snail feeds on both plant foods and small insects and microorganisms. Quite often you can see snails eating the foliage of aquatic and coastal plants. If the number of mollusks in a reservoir increases greatly, this is very harmful to the surrounding plants.

In the aquarium, the Common Prudovik can be fed with cabbage stalks, 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 the eggs are fertilized both by their reproductive products and by other snails.

At one time, the snail lays a large number of eggs, enclosed in transparent mucous clutches.

In an aquarium, breeding of the pond snail is difficult, since most of the laid eggs are eaten.

The Prudovik snail reaches sexual maturity when its shell grows to 20 mm in length.

CLASS Gastropoda Molluscs (Gastropoda)

In gastropods, the body consists of a head, trunk and legs. The leg is muscular abdominal part body, leaning 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); PRUDOVIKA 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. Lives on plants in stagnant bodies of water, in the same place where 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, often floating 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 middle lane 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 rocks and rocks. 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 the 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 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. It 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 bushes, 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. Lives in open places - meadows, swamps, near roadside ditches, on forest edges, but, unlike the reticulated 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, 30-50 mm long. 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.