The pond snail is ovoid. The small pond snail is a snail from the reservoirs of our country! Feeding, mineral supplements

Names: common pond snail, marsh pond snail, large pond snail, lake pond snail.

Area: Europe, Asia, North Africa, North America.

Description: pond snail, belongs to the pulmonary molluscs. The largest of the pond snails living in Russia.V recent years divided into two types - Limnaea stagnalis And Limnaea fragilis The appearance of the pond snail is very variable: depending on the living conditions, the color, thickness, shape of the mouth and curl of the shell, and size vary. The pond snail's body can be divided into three main parts: the body, the head and the leg. The body follows the shape of the shell, fitting closely to it. The shell is thin spiral (twisted in 4-5 turns), strongly elongated, with a large last whorl. The shell consists of lime, covered with a layer of greenish-brown horn-like substance. The head is large, with flat triangular tentacles and sitting at inner edge their bases have eyes. Tentacles are thread-like. The pond snail's mouth leads to the pharynx. It houses a muscular tongue covered with teeth (grater). From the pharynx, food enters the stomach, then into the intestines. The liver helps digest food. The intestine opens through the anus into the mantle cavity. The leg is narrow and long, muscular, occupying the entire ventral side of the body. The breathing hole is protected by a prominent blade. The circulatory system is open. The heart pushes blood into the vessels. Large vessels branch into small ones, from which blood flows into the spaces between the organs.

Color: The color of the legs and body ranges from blue-black to sandy yellow. The pond snail's shell is brown.

Size: shell height 35-45 mm, width 23-27 mm.

Lifespan: up to 2 years.

Habitat: standing bodies of water (ponds, lakes, river backwaters, canals, swamps) with abundant vegetation. It can live in slightly brackish water. The pond snail is also found in drying up reservoirs.

Enemies: fish.

Food/food: The pond snail feeds on rotting remains of plants and animals. It deliberately swallows sand, which remains in the stomach and helps grind hard food.

Behavior: the pond snail is almost always active. It crawls among the thickets, scraping algae and small animals from the underside of the leaves. The maximum crawling speed is 20 cm/min. It breathes air, the reserves of which are renewed by rising to the surface (6-9 times per hour). Pond fish, living in deep lakes at considerable depths, breathe air dissolved in water, which is filled in the respiratory cavity. When the reservoir dries, it seals the mouth of the shell with a dense film. It can freeze into ice and then come back to life when it thaws.

Reproduction: The common pond snail is a hermaphrodite. Cross fertilization. Lays eggs enclosed in transparent mucous cords, which it attaches to underwater plants and objects. Lays 20-130 eggs.

Breeding season/period: throughout the year.

Incubation: about 20 days.

Offspring: development without the larval stage. The eggs hatch into small pond snails with thin shells.

Literature:
1. Brockhaus F.A., Efron I.A. Encyclopedic Dictionary
2. M.V. Chertoprud. Fauna and ecology gastropods fresh waters of the Moscow region.
3. Virtual school"Bakai"
4. Great Soviet Encyclopedia

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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. 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.

Did you know?The snail's tiny brain is divided into four sections and is quite efficient. Scientists claim that these mollusks have the ability to make independent decisions. 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 of the family. 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. 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. In an 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. Natural environment The habitats of the ovoid pond snail are lakes and quiet rivers. He can live like coastal zone, and at depth.
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 with gray color 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 on great depth, are able to exist due to 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 lack hearing and voice, very poor eyesight, but their sense of smell is perfectly 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. The maximum speed 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 duration life of an aquarium pond snail is two years, in wildlife- 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 more warm 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, and sepia to them.

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 largest sea snail is considered to be the giant Australian whelk, 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.

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The shell is spirally twisted, without a lid. In some species (slugs) the shell is reduced. The ganglia are concentrated in the head region, forming the peripharyngeal nerve ring. A nerve branch extends from the right parietal ganglion to the accessory azygos ganglion. Pulmonary molluscs have one atrium, one lung and one kidney.

rice. 1.
A - top view, B - side view: 1 - mouth, 2 - cerebral ganglion, 3 - pleural ganglion,
4 - parietal ganglion, 5 - visceral ganglion, 6 - liver, 7 - pericardium, 8 - lung, 9 - heart, 10 - kidney, 11 - stomach, 12 - gonad, 13 - mantle cavity, 14 - leg, 15 - head, 16 - anus, 17 - additional azygos ganglion.

(Fig. 2) - one of the largest terrestrial mollusks in Europe. The spherical-twisted shell has 4-4.5 whorls, reaches a height of 5 cm, a width of 4.5 cm. The shell is usually yellowish-brown in color with dark brown stripes running along it. The color and width of the stripes vary. On the head grape snail there are two pairs of tentacles, one of which has eyes, the other serves as organs of smell and touch. It feeds on green parts of plants. By eating grapevine leaves and buds, it can cause harm to vineyards.

rice. 2. Grape
snail (Helix pomatia).

The grape snail is a bisexual animal. It has one hermaphrodite gland in which female and male gametes are formed. A hermaphroditic duct departs from the gland, into which the albuminous gland flows. After the confluence of the protein gland, the hermaphroditic duct expands, forming two gutters: a wide one for eggs and a narrow one for sperm. Next, each of the gutters is transformed into independent channels, respectively, the oviduct and the vas deferens. The oviduct drains into the uterus, the uterus into the vagina. In addition to the oviduct, the ducts of the spermatic receptacle and bags with calcareous needles flow into the uterus. The vagina opens with the genital opening in a special skin invagination - the genital atrium. The vas deferens passes into the ejaculatory canal, which penetrates the copulatory organ, which opens into the genital atrium. During mating, grape snails exchange spermatophores (packets of sperm), which are captured by the spermatheca. Fertilization will occur after mating. Eggs that enter the uterus are fertilized by foreign sperm coming from the spermatic receptacle. The formed eggs are laid in a burrow, which the parent first digs in the soil with its muscular leg.

In a number of European countries, grape snails are used as food.

rice. 3. Big
pond snail (Limnea stagnalis).

(Fig. 3) and small pond snail (L. truncatula)- frequently encountered inhabitants of our fresh water bodies. The head bears one pair of tentacles, at the base of which there are eyes. Hermaphrodites. During mating, just like in a snail, sperm are exchanged and eggs are fertilized by foreign sperm. They lay eggs in slimy cords that are attached to underwater plants and other objects. Development is direct, without a larval stage. Breathe atmospheric oxygen, therefore they periodically rise to the surface of the water in order to gain a portion of air.

The size of the shell, its shape, the color of the leg and body are characterized by strong variability in the large pond snail. For example, the color of the body and legs can vary from blue-black to sandy yellow. The length of the shell of a large pond snail can reach 7 cm. Great pond snail omnivorous, feeds not only on plants and small animals, but can eat dead plant debris and animal corpses.

rice. 4.
A - Arion rufus,
B - limax maximus
(Limax maximus).

A collective group of terrestrial pulmonary mollusks with a partially or completely reduced shell (Fig. 4). On the head, next to the mouth opening, there is a pair of labial tentacles, and on top there are ocular tentacles bearing eyes. The narrowed portion of the body between the head and mantle is called the “neck.” At the bottom of the neck, a gland duct opens that secretes mucus. In addition to this gland, numerous mucous glands are scattered over the entire surface of the body, so the entire body of the slug is covered with mucus. The main purpose of mucus is to moisturize the skin. On the right side of the neck is genital opening. The mantle looks like a flat thickening on the dorsal side of the body. Near the right edge of the mantle there is a respiratory opening leading to the pulmonary cavity. Near the respiratory opening on the right edge of the mantle, the anus and excretory pore open. Slugs are bisexual animals. During mating, male gametes are exchanged. Eggs are laid in moist, shaded areas.

Most slugs feed on plants, lichens or fungi. Predatory slugs feed on oligochaetes or other types of mollusks. Active at night, stay hidden during the day. Slugs settling in areas occupied by agricultural crops can cause significant damage to crop plantings. For example, the field slug (Agrolimax agrestis) eats sown grains and seedlings of winter wheat and rye, and the netted slug (Deroceras reticulatum) causes great damage to the harvest of tomatoes and cabbage.

Description of classes, subclasses and orders of the Mollusc type:

• Class Gastropoda

  • Subclass Pulmonary (Pulmonata)

Pond snails are freshwater lung mollusks distributed throughout the world. This family includes a huge number of species, but among them the most famous is the common pond snail, which has the most large sizes.

Large individuals reach 7 centimeters in length. These snails live in ponds, small lakes and river creeks from spring to autumn.

Large mollusks crawl quite interestingly along the bottom of the reservoir and aquatic plants. The most large number pond snails are found in mid-summer among water lilies.

These mollusks are omnivores. Crawling over aquatic plants, they scrape off algae from them with the help of their radula, and at the same time eat the smallest living creatures that come across on the way. Pond fish are very voracious; they eat not only plant and animal food, but also carrion.

Pond snails often rise to the surface of the water, suspend themselves from the water film from below using a wide sole, and swim slowly in this position. Pond snails rise to the surface of the water for a reason. Although they live in water, they breathe, like all pulmonate mollusks, using their lungs, which is why they must rise and take air into their lungs. When a clam takes a breath of air, its respiratory opening, which leads into the pulmonary cavity, is wide open. The presence of lungs suggests that the ancestors of pond snails are land mollusks, and they returned to the water a second time.

Pond snails are freshwater mollusks.

Reproduction of pond snails

During the mating process, pond snails mutually fertilize each other, since they are bisexual creatures. Pond snail eggs are long, transparent, gelatinous cords that are attached to a variety of underwater objects. The eggs can even attach to another pond snail.

Caviar has complex structure– the egg cell is immersed in a mass of protein, and on top it is protected by a double shell. In turn, the eggs are in a mucous mass and are dressed in a special shell or cocoon. A cord extends from the inner part of the shell, the second end of which is attached to the outer shell of the egg, that is, it turns out that it is suspended from the wall of the cocoon. This complex structure of eggs is characteristic of many species of mollusks.

Thanks to this structure, the egg is provided with nutrients and protected from exposure external environment. Inside the eggs, pond snails develop without the free-swimming larval stage. Most likely, this structure of eggs in pond snails is due to their connection with land ancestors, where such adaptations were more important than in water. The size of the clutch and the number of eggs in it can vary significantly. Sometimes there are up to 270 eggs in one cocoon.

Pond snails differ markedly from each other, and their size, color, thickness and shape of the shell can vary significantly. There are both large individuals and almost dwarf ones that have not matured due to poor nutrition or unfavorable external factors. In some individuals the shell consists of thick walls, while in others the shell is very thin and fragile, it breaks at the slightest impact. The curls and shape of the mouth vary greatly. The color of the body and legs can vary from sandy yellow to blue-black.

Thanks to this tendency for pond snails to vary, a huge number of varieties of mollusks have formed within the species. Therefore, it can be difficult for even scientists to determine whether a particular individual is simply a variety or a new subspecies.

Species of pond snails

In our reservoirs, not only common pond snails are often found, but also another species - the long-eared pond snail. In addition, the marsh pond snail and the egg-shaped pond snail live in stagnant water.

By 6-7 months, small pond snails reach sexual maturity, and they live for about 2 years. An egg cocoon can contain from 4 to 25 eggs. Young individuals develop over 10-20 days.

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, 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 a pond snail, sticking its leg and head with tentacles out of its 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, 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 water bodies, 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) The garden snail has a cube-shaped shell, 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 the Leningrad and Perm regions. Often causes damage to garden, fruit and berry crops and ornamental plants, scraping out the leaf tissues 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 the forest and forest-steppe zones of the 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 turns 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. It lives in open places, avoiding forests and bushes, 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 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.